Just that - what do you like and/or dislike about them? I have noticed trends over the years, and often wonder what changes were made for the sake of change, or what people find actually useful. The considerations can be technical, aesthetic, or anything else.
I was not online much in the pre-internet BBS days, mostly because my parents were worried that I would blow up their phone bill or otherwise get into trouble with it. And I mostly missed UseNet, showing up in the early naughties when it was mostly used to transfer binaries.
My first big internet discussions were on email-based mailing lists, using majordomo. I liked the text-based approach. It was single message or digest, and I found single easier to follow.
Most useful to me so far are bulletin-board style forums made with phpBB and the like. They make integrating non-text data easier, and offer more ways of organizing content.
What I use online these days are mostly what I call “whitespace forums”, because there is just so much wasted space. The topics are always far apart vertically, and posts crammed into the center leaving vast horizontal margins. More features for linking content from elsewhere, such as onebox and “share on social media” things.
What else is there? Or should there be? If you were going to use something to make a forum, what would you use, and why?