@matrix come on, you can think this through.
how is rich text implemented? html or markdown currently.
what does pleroma do with the markdown and html? parse it.
oh wait, you said html, thats a lot of allowed tags. what does pleroma have to do to keep it safe? whitelist the allowed tags, keeping in mind to maintain compatibility with current posts as well as to allow enough to be usable
both the parsing stage and the "allowing enough to work" stage are incredibly difficult to get right, and we've seen this with the spinning text shit, the <span class/> shit, and possibly more to come down the line. it's something i dont want to have to deal with, and i'm biased as a past twitter user and a current email user: plaintext is more than enough for microblogging