Lol same. I think it’s probably because commenting is more like normal conversation; you’re responding to other people in ways that are specifically meaningful to the circumstances. Writing is sorta like talking to the void in my mind. I find I spend much more time thinking and checking and re-reading to make sure I’m appealing to my imagined audience, rather than just contributing a sentence or two to a conversation where the audience is a bit more concrete.
Almost certainly not. It’s common in some communities for people to write their own image transcriptions.