It would be great if you could see a list of who is currently using the forum.
It would also be great if you could "mark" unread posts within the forum.
Usernames: The option when registering for a username (nick name).
On my forum, members must be logged in to use it, so showing "who is logged in" would be a nice feature.
The second point on my "wish list". This would be transform Wix forums massively. The only way of seeing new posts now is to either have notification all the time (annoying emails etc) or "show new posts" turned on. The problem with the latter is some of my forum is private for a selected few, and those posts don't get filtered out of "show new posts" and everyone gets to see them.
Finally a username option when joining as a member. Some members would rather not show their identity.
Please work on these Wix. Thanks