Jaymin,
First, please realize that I won't be able to keep up with comebacks. So, after this suggestion, I won't necessarily feel motivated to respond or reply to Mr. Unknown (MU).
Since I don't know Mr Unknown's (MU) personality, I don't know if he is desirous to learn, or if he is faking curiosity in order to assert his own opinions.
1) how does MU mean "Paul is/isn't speaking of how to become saved." Does he refer to the Letter? or does he refer to this particular sentence? And then there is the question of what he means by "salvation." Does he view salvation as "getting saved," as in a MOMENT when a person crosses the divide? or of the whole process that starts at some moment and ends in glory?
Romans is, to begin with, the Christian "gospel presentation", at least from ch1.18 through ch.11. And what is "the gospel"? It is NOT "how one gets saved." That is a practical question, an application of the gospel, not the gospel itself. The gospel itself is the proclamation of what it is that God has DONE to save sinners. Sinners are justified through FAITH in the gospel message. Not when they pray a prayer, and certainly not when they do law-keeping. Prayer and obedience are inevitable products of a believing heart, but they are not actions that move God to extend justification. He justifies those whom he effectually "calls", Rom. 8:30, which "called ones" are reconstituted and enabled to believe.
Now the fact is that one can take Paul's "gospel presentation" and break it up into LAW and GOSPEL. Law condemnation precedes gospel salvation, and these two "parts" are most obvious in Paul's language when he says, first of all, ch1:18, "WRATH REVEALED," and then ch3:21, "RIGHTEOUSNESS REVEALED."
WHY does anyone need "good news" or "gospel"? Because there is a boat-load of BAD NEWS that has to be acknowledged, or God's salvation is not attractive. The sinner doesn't "need" it, in his own mind. Factually, he does, of course, but until he is forced to admit it, he will never seek God's solution.
So, any attempt to understand Romans that will not or cannot see Paul's thought progression, and that this is a larger section dealing with the facts of WRATH, not the facts of RIGHTEOUSNESS, may well make interpretive errors. And MU is off track.
Paul is not speaking, in the place he describes, about "how to get saved", or even the gospel, in its narrow conception. So, MU has make an accurate statement when he described our understanding of what Paul is saying. He understood you, and the "hinge" of that argument.
Second, this may be the "first instance" of this verb, however, it is certainly not the first introduction of the word-complex, which includes noun forms. That would be Paul's thematic or purpose statement in ch.1:16-17. There, the word dikaiosune or "righteousness" is used, a cognate term to verb dkaiow, the future-passive-3p form which is used in 2:13.
The use of a certain "word" cannot be assumed monolithic, as if it can only be used in contexts that state ideas positively. This is a completely unsupportable position. How else could Paul say, "by the works of the law shall no flesh be justified" (Gal. 2:16)?
So, MU's statement that he "finds it difficult to believe" this is the direction of Paul's thought in Romans based on how he thinks Paul MUST use a certain verb is merely a preferential statement; "I don't THINK" is not an argument, but is an admission of a lack of one. By "peppering" you with references to other texts, he has made no attempt to handle Paul's own argument here.
The texts he adduces are references to God's most certain and just final accounting. Interestingly, the Romans verse makes no mention at all of the content of that meeting, an omission that does not help MU's cause. The other verses in the Corinthians correspondence are not in contexts that deal with justification or the beginning of individual redemption in any way. So, it makes virtually no impact on my interpretation of Rom 2 to admit to the principle that God will bring every fact (or ACT) into judgment at the last day. In fact, 1 Cor. 3:15 is even worse for MU's position, because it states that the individual concerned WILL BE SAVED, though barely, as it were.
Such an assize has no bearing on whether a person will enter heaven or not. If it did, then we should have no confidence that those without "good" works, including infants and the death-bed-converted, were accepted. So much for the malefactor on the cross; he's lost too. So, the idea of justification in the salvific sense by works, besides being explicitly repudiated in Galatians, is done away with in this very section, the final verse, Rom 3:20. It is the conclusive statement to the whole indictment of Jew and Gentile alike.
And in the surrounding texts: "NO ONE IS RIGHTEOUS!" Rom 3:10. Rom 3:28. "Therefore we conclude that a man is justified by faith APART FROM the deeds of the law."
Why is 2:13 "hypothetical"? Because 1) it is not proper to be divorced from the context, 2) set against the context, 3) set against the weight of Paul's propositions made in various discourses on the subject of salvation; and finally 4) must actually be HARMONIZED with the texts he proposed respecting final judgment for the believers, which rather seem to teach not a question of destiny, but the quality of reward.