So I'm going to condense all my suggestions into one thread just so I don't end up making a bunch of threads all at once, sorry if any of these have already beem suggested, but I hadn't seen any of these yet!
Basic color formatting for posts
Additional html customization for threads in the forum, may need to be restricted to a set palette to prevent abuse, and ease accessibility, readability, and proper display on dark/light mode.
Image embed button
Something I'm surprised wasn't already a feature and made me dig around a lot of old html knowledge in my brain to figure out how to imbed images. A quick shortcut button on the forum posting toolbar would be a nice QoL of life feature for less html savvy users.
Forum game forum
Would keep clutter out of other forums and prevents threads from being drowned out, helps community engagement.
Forum signatures
Would be a nice user customizability and qol feature, such as providing a space to link user shops, graphics, or important information about themselves in a more conveniently readable format than user profiles themselves.
Thread bump button
Great qol feature for sales and art threads so users don't need to manually bump threads, but may need to be set on a timer or restricted in some way such as only to the original poster and a certain amount per day (say once every few hours) to prevent abuse of the feature. This can also be disabled on threads past a certain age (say several months) to prevent necrobumping of old topics.
Thread subscriptions & thread subscription management
Currently, we don't receive notifications when other users post in our forum threads, this is something I'd love to have the option of, as well as being able to follow other threads on site by way of an opt-in thread subscription feature.
Additionally, having the ability to see what threads I am currently subscribed to via something like a list under account settings and the ability to mass manage my thread subscriptions would be amazing for qol.
Ability to lock/close own threads.
This is a feature I could see potentially abused if one were simply able to delete threads, but a good compromise would be allowing the original poster of the thread to close/lock a thread when they are finished with it, allowing the thread to be preserved. This also protects threads against necrobumping especially on old topics.
This could be restricted similarly to only allow the OP to close/lock a thread of their own and disallow them to reopen the thread without contacting a moderator just to prevent any potential abuses of this.