Mobile support is the biggest feature for me. I'm surprised how many forums don't simply do width:90% and such with the comment field. I'm only on a PC at work,

Mobile support is the biggest feature for me. I'm surprised how many forums don't simply do width:90% and such with the comment field. I'm only on a PC at work, so that leaves out forums for socializing. A lot of the remaining forums just don't play well with Reddit/FB. Things like a specific community or game. Things with some quality control (also including Something Awful). Or places like 4chan. Though out of all of these, I'm surprised that 4chan/8chan users have set up a colony on Facebook, but they don't expect to stay there. I think Discord has some places of interest but there seems to be a very high barrier to joining unknown servers, unlike IRC.