Sorry, my mind has been corrupted by the "popular" development crowd.
Improved banning system & infractions
It would be really cool if the future releases of NodeBB would feature an option to give infractions to other members who have broken the rules. (this option would be available to forum moderators). It would be also great if certain groups would have the ability to ban/unban members (also forum moderators).
I also think that the category permissions section should be moved under the groups & users management section in ACP. At the moment, it is really tedious to set permissions for each group in multiple categories (Each time I'd have to navigate inside the category and fill in the checkboxes for every category when a new group is created.).
Tbh, it's hard to explain, but I hope you get the idea.
@markkus You may want to take a look at this plugin