The question is - can you politely correct someone's spelling without being thought of as a troll?
I believe the answer to that question is no. I have tried in the past and failed many times. I am a grammar nazi as well, but NO! I cant correct people's grammar!
It's been said, "dont be a dick." :p
I think it's based on the context. If they accidentally missed an apostrophe and used "its" instead of "it's," mayyyyybe you should just let it slide.
But if thery're like mahsing on a kedsyp[board it's probably fine to correct them even if they get pissy
Or of course you can tell the drunk typers to go be drunk elsewhere.. this occurred on a thread I was posting in earlier... It was quite hilarious.