Seeing to the other comments, I couldn't help myself, and decided it was necessary to write a detailed response to these claims.
(1) Modern English speakers would naturally read the verse as indicating two individuals named Yahveh . . . [but] the way they wrote and understood Hebrew may have been different than the way we do today.
(2) The medieval commentators provided many Scriptural examples of this kind of reference, such that there is no need to assume that there is someone else with the same name being referred to...
1. Modern English Anachronism?
I should start by stating, the text does not indicate 2 YHWH's but 2 distinct people who share the 1 name (not just title) of YHWH. Definitions aside, let's get into the historical evidence for the claim being made.
As was claimed above: if we read the statement in Genesis 19:24 (which for some reason was posted in Hebrew as if that helped at all), and come away with there being 2 YHWH's, then we're actually being anachronistic by reading our "modern" English phraseology back into the Hebrew text.
Not only is there no evidence that supports this claim, but the actual evidence sets itself squarely against this claim. As a matter of historical fact, some of the earliest interpretations we actually have of this passage affirms that the passage is indeed speaking of 2 distinct persons.
To start off Jewish Targums (probably 8-10th century CE) state:
And the Word of the Lord Himself had made to descend upon the people of Sedom and Amorah showers of favour, that they might work repentance from their wicked works . . . He [the Word] turned (then), and caused to descend upon them bitumen and fire from before the Lord from the heavens.
(Targum Jerusalem, Genesis 19:24)
-- and if we go back in time just a little further (to about the 2nd-3rd century CE), you might notice a familiar argument (which we will get to next):
The heretic raised the question: It should have stated: From Him out of heaven . . . Leave him be; I [Rabbi Yishmael] will respond to him. This is as it is written: “And Lemech said to wives: Adah and Zillah, hear my voice; wives of Lemech, hearken to my speech” . . . [then] rather, it is the style of the verse to speak in this manner. Here too, it is the style of the verse to speak in this manner.
Sound familiar? That would almost seem to support the claim against there being 2 persons as the most ancient, but did you notice the problem? The very fact that this was being disputed among the Jews of that day shows you that there were people that interpreted the passage as it referring to 2 distinct people (hence why the poor soul was being labelled a heretic).
But wait, there's more. The text goes on:
From where did you hear this interpretation? The launderer said to him: I heard it at the lecture of Rabbi Meir.
You heard that right. There were even Rabbis teaching the interpretation of there being 2 distinct persons in this passage as far back as at least the 2nd century CE.
"Rabbi Meir was a prolific scholar who studied under Elisha b. Abuya, R. Ishmael and R. Akiva." (sefaria.org)
That poses a very difficult problem for the proponent of the view that this is a 'modern English anachronism' even though there were Rabbis, who were well respected, and who were fluent in Hebrew and Aramaic, publicly proclaiming this view. The Rabbis, and likely many other Jews (and more than likely their ancestors), were very clearly teaching that there was a YHWH on earth (that spoke to Abraham) and a YHWH in heaven (from whom the fire came).
It's also important to note that the earliest Christian authors such as Justin Martyr (Ch. 56), Irenaeus (para. 1), Tertullian, all universally read this passage as referring to 2 persons. Oh, and none of them spoke English.
Now that this is utterly debunked, let's move on to the next claim.
2. Third Person Idiom?
The very least I can say about this argument is that, at best, it is trying to be faithful to the language that's used elsewhere in Scripture, and at worst, it's completely misunderstanding the context of Genesis 18-19, and ignoring the passages where God Himself comments on the events.
This is by far the most common rebuttal to the view that there are 2 distinct people in Genesis 19:24, it goes something like this:
In other passages, people will often refer to themselves in the third person, which is simply idiomatic phrasing. Therefore, this is actually just Moses using a common Hebrew idiom that's used elsewhere in the Bible.
The strongest example of this is 1 Kings 8:1 where it is written:
Now Solomon assembled the elders of Israel and all the heads of the tribes, the chief fathers of the children of Israel, to King Solomon in Jerusalem, that they might bring up the ark of the covenant of the LORD from the City of David, which is Zion.
1 Kings 1:18 (NKJV)
You don't believe there's 2 king Solomons do you? Of course not.
Well then, let's first start with the argument that "people will often refer to themselves in the third person".
No doubt Scripture has numerous examples of individuals referring to themselves in the third person, a good example is Genesis 4:23, 1 Samuel 20:12-13, and Esther 8:8 (the list goes on). Did you notice something common to each of these passages? In every single one of these passages the person being referred to in the third person is the person speaking.
Lamech said to his wives: “Adah and Zillah, hear my voice; you wives of Lamech, listen to what I say: I have killed a man for wounding me, a young man for striking me.
Genesis 4:23 (ESV)
And Jonathan said to David, “The LORD, the God of Israel, be witness! When I have sounded out my father, about this time tomorrow, or the third day . . . But should it please my father to do you harm, the LORD do so to Jonathan and more also . . .
1 Samuel 20:12-13 (ESV)
But you may write as you please with regard to the Jews, in the name of the king, and seal it with the king’s ring . . .
Est 8:8 (ESV)
But does God refer to Himself in Genesis 19:24? No.
As I've demonstrated, every one of these passages, where the third person "idiom" is used, the subject is always the one speaking. In fact this is why I believe this argument commits a fatal error by trying to equate 2 distinct Hebrew linguistic features into 1. The particular form of speaking where a person addresses themselves in the third person is one, and another is the writing style where the subject (being spoken about, not the one speaking) has their name in place of the pronoun "himself" or "themselves".
i.e. John Doe told his son to buy groceries, to bring them to John Doe at his house.
Anyways, the only two clear examples of this are 1 Kings 8:1, and 1 Kings 12:21. That being said, did you notice something about these two passages that's different from Genesis 19:24? Let's look at these passages.
Then the LORD rained on Sodom and Gomorrah . . . from the LORD out of heaven.
Gen 19:24 (ESV)
compare that to:
Now Solomon assembled the elders of Israel . . . to king Solomon in Jerusalem . . .
1 Kings 1:18 (NKJV)
When Rehoboam came to Jerusalem, he assembled all the house of Judah . . . to restore the kingdom to Rehoboam the son of Solomon.
1 Kings 12:21 (ESV)
I will agree, the phrasing does seem quite similar. However, similar phrasing should never determine the meaning of a passage, rather its context should determine its meaning.
Suppose you knew that King Solomon was in East Manasseh, wouldn't it be odd if the verse then said "to King Solomon in Jerusalem"? In fact, you would rightly conclude that there are actually 2 king Solomons in that case. One in East Manasseh and one in Jerusalem.
And suppose you knew Rehoboam was the son of Jerubbaal, wouldn't it be odd if the verse then said "to Rehoboam the son of Solomon"? You get the point.
Case and point, the YHWH that was just standing physically in front of Abraham (Genesis 19:27, Genesis 18:22, Genesis 18:1-2) in the form of a man, is now reigning fire and brimstone, not from earth, but from the YHWH out of the heavens. Note that the phrase "out of the heavens" is not speaking about the fire and brimstone alone but also speaking of YHWH, the person. In other words the action of the reigning of fire and brimstone by YHWH is being done "from the heavens" by a YHWH that's in the heavens. Whereas the other YHWH is still on earth.
Contextually there is no parallel to this passage. We cannot simply defer it to "a Hebrew idiom" (hence the disputes amongst Jews even after the time of Christ) merely because we see similar language being used. When we read the whole context, it becomes clear that there is a YHWH standing on earth, and a YHWH who's being commanded to reign fire and brimstone out of heaven on Sodom and Gomora.
Not only that, but is it just a coincidence that in almost every single passage that God references the destruction of Sodom and Gomora he just happens to be speaking in the third person? I think not. It seems to me like a very convenient way to get out of having to deal with the fact that there's 2 distinct persons who are both referred to as YHWH in Genesis 19:24.
And Babylon, the glory of kingdoms, the splendor and pomp of the Chaldeans, will be like Sodom and Gomorrah when God overthrew them.
Isa 13:19 (ESV)
As when God overthrew Sodom and Gomorrah and their neighboring cities, declares the LORD, so no man shall dwell there, and no son of man shall sojourn in her.
Jer 50:40 (ESV)
I overthrew some of you, as when God overthrew Sodom and Gomorrah . . .
Amos 4:11 (ESV)
Very convenient that all of these passages just happen to be in third person.
I agree with the Targums, and the ancient "heretic" Rabbis, and the earliest Christians of the Church, that the Angel of YHWH (who is also YHWH, and the Son) reigned fire and brimstone from YHWH who was in heaven (i.e. the Father). Proving that YHWH is identified with 2 distinct persons who share the 1 name.
Lastly, if you're an honest unitarian who loves truth, stop using Deuteronomy 6:4. Unless you can prove to me that men and women become like Siamese twins after they have sex (Genesis 2:24), it's perfectly and undoubtedly reasonable for a sane person to read the Hebrew OT, and see echad as "compound unity" and not "absolute singularity" (i.e. 1 person).
Have a blessed day.