I'm an English teacher, so yes, grammar matters to me, but not so much on social media/PC, etc. particularly. I'm as guilty as anyone of typing quickly, not proofreading, and hitting submit. Sometimes I notice my error and fix it right away, and sometimes not. That's okay. This isn't formal writing and we aren't getting a grade. We all do those things.

I do cringe when I see writing completely devoid of punctuation, rampant with so many spelling and grammar errors that it takes several readings to figure out what the heck a poster is trying to say. That is either complete carelessness or near illiteracy; either way I cringe. I'm not one to criticize others openly about it though. That's just not kind.

My one pet peeve is people who write posts in text-speak. Keep that craziness on the phone as far as I'm concerned. Consider the media you are on and your audience. At least attempt to write out your words, use a capital letter at the beginning of your sentences, and some form of punctuation at the end when you post to threads. Otherwise it is almost completely unintelligible.