These kinds of errors tend to completely throw me off. As a non-native speaker, then/than, your/you're and they're/there/their "sound" very different to me. Here's what happens if I get caught off-guard reading your sentence:

If some one comments on your grammar rather then you're... "Rather" looks odd there

... then you're reasoning it means you... Missing period?

... then you're reasoning. It means you won. Wait, what?

If some one comments on your grammar, (rather?) then you're reasoning. It means you won. That makes no sense! How is it that you are reasoning if someone comments on your grammar?

And by the time I re-read the sentence the third time to finally get it, I usually lose track of what's being said, and either re-read the whole paragraph, or just skip reading the rest. (Or in the case of chronic terrible spellers/grammar-ers, skip their posts entirely.)

So I'd like to take issue with your premise that you win if someone comments on your grammar. If you use terrible grammar, then for every person who comments on it, there are a few more (like me) who won't bother getting to the reasoning, and won't feel bad about it. That said, I'd like to request you to also put "some one" in bold ;)