I rarely get called "grammar nazi". As a German I would find it slightly offensive. Also, in general, I don't correct others if they don't ask me. Yes, I did call out "fake native English speakers" from time to time in the past or point to typical native English speakers mistakes. But nobody is immune from making typos. So, if I'd point out that someone mixed up they're, their and there, then definitely next time, I make this kind of typo, someone would send me a message telling me that I made this very mistake. Also, the most educated and eloquent native English speakers here make typos but I refrain from telling them. It would come off as rude since I'm a mere learner and my own mistakes are all over the place. Also, in my native tongue German, I only correct if people specifically ask me for it. So, if a learner says that I should correct every single mistake, I do that. If they only want to have big mistakes pointed out I do that. And if they just want to communicate with me but aren't interested in corrections, then I don't give any corrections.