I've read that people are using that as a sign that they aren't writing with AI, however I imagine it's easy enough to ask the AI to not capitalize and to use typos.

fair point, i do that only because i'm very used to it. i may introduce an option to auto-capitalize, and maybe different fonts to improve readability (and accessibility), especially for people with dyslexia

He does it for attention and your comment just gives it to him.

it comes from IRC / BBS times, so the trend is 30+ years old.

have you really not been online long enough to be able to parse communication without unnecessary markup

The missing punctuation at random times was infuriating. Never fun when you have to re-read a sentence because the word without punctuation is itself also a word.