I like the premise, and the free-form layout of following topics, vs. maybe following a specific thread in a subforum. This feels sort of like a "Medium"-light
A couple of improvements from my perspective would be to implement category blocking alongside member blocking. For members that join and simply want to follow uplifting, positive, and/or non-confrontational categories; there can be some anxiety when opening the site and greeted with a full screen of political posts due to a member's choice to post a lot at once and tag them with categories that might bleed over. I saw this last week one day when I opened the site and the whole screen was political, even though I haven't chosen any politics categories to follow.
A second improvement (and this may exist, but I have not yet figured out) is being able to post photos inline with text, rather than after all the text has been entered. The little photo posting icon remains at the bottom of the text in a post and seems like it should allow an image to be inserted, then begin a new paragraph.
I have followed quite a few categories that I normally would not have in a topic-specific message board. For that, I'm very appreciative; keep up the excellent work!