First time poster here (I'm a secret lurker and often smile at posts - or ooh and ahh with the best of them). I'm an editor/proofreader and author, so I interact on social media a fair bit - and wince regularly (my DD sometimes asks if I've developed a tic). However, I would never, ever, correct punctuation, spelling, grammar etc. uninvited. As others have said, autocorrect can be a plague, fat fingers and small phones don't help, and - at the end of the day - it's social media, so does it really matter? I'll carry on silently twitching until they become a client... :D