In the MT, the first sign that a group of letters is a name is the orthography.
If a group of letters that is not obviously a noun is written without spacing and functions as a subject or object of a sentence then it is likely a name.
The second sign of a name is syntactic. If splitting a group of letters into component words, or reading a name as a noun results in incongruous syntax, as would
ומלכי צדק מלך שלם
which would read "And my king was correct, the king of wholeness [peace]", then it is likely a proper name.
The third sign is semantic. If interpreting a string of letters like שלם as a noun results in incongruous semantics then the letters are probably a name. In this case the incongruity is use of an abstract concept, wholeness, peace, with "king", not something that the MT does.
The fourth sign of a name is the translation tradition. If the group of letters is traditionally considered a name then there is no reason to translate the components of the name.
A reason not to translate Hebrew names, which are often complete sentences in and of themselves, is the confusion that this would create for the reader. The reader would not be able to distinguish between a name sentence and the rest of a verse without special punctuation.
The reason for not translating Hebrew names, as opposed to names like "Red Cloud" that we do translate, is that Hebrew names are generally complete sentences in an of themselves, rather than noun phrases that are easy to distinguish as probable names.
A final reason is that Hebrew names that are sentences, or have special meaning, are thought of as people or places when speaking the language, rather than as the meaning of the names. My children are:
- Yair (Arabic: Munir) "He will shine"
- Emanuel "God is with us"
- Naomi ?
- Shifra ?
- Yeshurun "Straight"
- Benayah "Son of God"
- Yedidyah "Friend of God"
- Elisha "My God listens"
- Emunah "Faith"
- Mevasseret "Gospel"
These are normal names for normal kids in Hebrew throughout the ages. No need to translate them. None of their friends even think about the meaning of the name when talking with them.