A recent question of mine, How is TLDR used? led to the suggestion that a discussion of the acceptability of such abbreviations in EL&U answers was really a meta question, so I am raising it here.
We are told in How do I write a good answer?: "We don't expect every answer to be perfect, but answers with correct spelling, punctuation, and grammar are easier to read." In my opinion, such expressions as tl;dr, AFAIC and YMMV do not show 'correct grammar' in terms of the standard language. More importantly, their meaning is opaque to quite a few of the "linguists, etymologists, and serious English language enthusiasts" for whom this site is intended.
These terms are now commonly used in chatrooms, social sites and informal private emails and texts, and discussion of their meaning and appropriateness is in order. Their use in serious answers is not - that's my belief. I'd be interested to know what others think.