trwnh:
Topics can be split
In addition to splitting topics, topics or their posts can also be merged into another topic. The UX for this is quite variable; sometimes entire topics can be merged into another, sometimes a certain range of posts within a topic (post 5 .. 10 from 15 posts), and sometimes a selection (post 5 and 10 from 15 posts or just a singular item post 5 from 15 posts).
trwnh:
Topics exist in a category
For #Flarum topics can also not exist in a Category (we call them tags and that extension is optional, like all of our extensions). Even when using a Category, once the Category is deleted, we do not hard delete any topics contained within but unlink them, making them less visible but still existing within the Forum.
Regardless, to us, Topics CAN exist in a category, it's not required.
trwnh:
Users can be followed for posts and topics
Users can be messaged directly
This sounds as if this is a given, I don't think it's guaranteed in every Forum software. But if can implies optional, then