An internet forum (presumably we're referring to a public forum here) is a very different communication medium than email (especially when used in a professional context)
Tons of visual clutter with all kinds of rectangles nested inside each other all over the screen with little apparent purpose for any of them. Join dates of users are given higher visual precedence to the date a comment was made (why is the join date of a user even visible on a discussion page at all?? That's pointless clutter!) 90% of users attaching signatures to every comment they leave with the signature body being longer than whatever remark they left, and often being filled with shitty animated gifs that look like they were stolen from somebody's geocities page.
It's a trash medium. Fundamentally flawed. Trying to fix typical PHP forums is like trying to polish a turd.
Not really. Take a look at any email discussion like the Linux kernel mailing list or the git mailing list. Same thing with newsgroups (usenet).
good lord, how old are you?