I'd disagree that regular users don't have any problems with it. One very common problem I've seen is a conversation like "How old are you?" "21." which Markdo

I'd disagree that regular users don't have any problems with it. One very common problem I've seen is a conversation like "How old are you?" "21." which Markdown interprets '21.' as a list and renumbers from 1, leading to: "How old are you?" "1." Another problem is that single linebreaks are ignored. Things like song lyrics and ASCII art get messed up, and some people even use single linebreaks for paragraphs. And even if you do use two linebreaks for paragraphs, there's still the problem that copy/pasting text will eliminate paragraph breaks since they're copy/pasted as one linebreak. I could go on, but the point is that Markdown is honestly not a very user-friendly way to format text on a discussion website.