You might enjoy Ascendant. It's not MHA/BNHA-based, but it is all about superpowers. It takes place in a twisted academy for mages (our word for people with powers) where the faculty is generally more interested in getting the students to fight each other than they are actually teaching them anything. Power levels are on the absurd level, so pretty much any kind of power you want to make should be perfectly fine. You can pretty easily change the setting in big ways as the game's pretty much focused on changing the world rather than derpy academy shenanigans.

For the specific things you requested:
- Is Proboards
- Has Discord
- I post all the time and my limits tend to be more about how quickly my partner's post
- I can't guarantee belonging, but my members tend to love on new people as long as they don't make a complete ass of themselves

Hope to see you there!

Hey there, Ginger~!

Perhaps you would like to give The Duality of Man a chance? We're a modern fantasy role-play that heavily enjoys supernatural concepts and can even support hero-esk characters with our plot. Our group is friendly and laid-back, all of us usually being up for plots and threads. We have been on ProBoards since the beginning, TDOM actually meeting its first year mark in a few months. Our Discord is open for anybody, having an extensive list of channels designed for your convenience.

Our plot itself takes place thousands of years after a war that divided the various supernatural creatures of our world. Another war has began, with sides each having a different definition of what would be beneficial to the world in its current state. Some side with the strict Assembly of Phantoms, a prominent terrorist group who believes a utopia promised by their leader while others support the Terror Response Syndicate who attempt to maintain peace among the general populace.

While I understand that I can not personally promise belonging, I will give you some insight on the community itself. As stated, we are laid back and are understanding towards the absence of fellow members. We are best defined as a group of gamers and self-proclaimed nerds; at least the majority from my knowledge. As expected, we enjoy the art of writing and role-play. Most members even stalk the bios watching for the latest in characters because of our craving for the activity.

Either way, I wish you luck on your search~!