First, the original Greek had no commas - NA28 and UBS5 have published their text without commas. So, a better way to state the question is to focus on the word, μηδὲν (meden), an adjective in the accusative neuter singular, that here means, "nothing" or "without".
The question can be restated as, Is (1) μηδὲν (meden) the object of the verb ἐσθίετε (esthiete) = eat; or is it (2) the object of the verb ἀνακρίνοντες (anakrinontes) = inquiring. Of these two possibilities, we would have the following translations:
- Everything in the meat market being sold, eat nothing; inquiring on account of conscience.
- Everything in the meat market being sold, eat; without inquiring on account of conscience.
While both are technically possible, it only takes a brief examination of the first option to realise it makes no sense for several reasons:
- The first clause, "Everything in the meat market being sold, eat nothing" is almost meaningless as it amounts to a complete prohibition of anything sold in a general market.
- The second clause, "inquiring on account of conscience" is also devoid of meaning as it instructs nothing, unless we make the farcical assertion that we are to eat nothing from the market but still making extensive inquiries for the sake of conscience. Why would one bother to ask if one is not permitted to eat anything anyway?
Therefore, the only way for 1 Cor 10:25 to make any rational sense is the second possibility listed above - we may eat anything sold in the market but do not inquire about whether it has been offered to idols so that your conscience will not be offended. The second option is that consistently adopted by every translation I could find and is the sense assumed by all commentaries I consulted.
Lastly, the second option is also consistent with the verses immediately before and after.