Have a read of this:
Posts about moderation will nearly always be off-topic in the thread where the moderation occurs. You should open a new thread like this in the Roon Community Section if you want to discuss moderation.
Moderators split threads when a discussion acquires a sufficient audience to justify a new thread in order to avoid multiple conversations about different things in the one thread. The idea is that users should be able to follow a discussion in its own thread, not have to piece it together through previous posts. Some forum software uses nesting to accomplish this, but Discourse doesn’t do that. When a new thread is split off, there is a link in the original post which can be followed by those interested.
Edit: Most folk who’s posts are split into new topics recognise that the discussion has expanded and are happy to have a separate thread for the new discussion. It’s not intended to be a criticism of anyone, just a thread management thing.
One option that Discourse does have, but which is a bit hidden away is ‘Reply as a linked topic’. To access this, start a reply to a post in the usual way and click the pencil in the top left corner. You will see this option, which is an easy way to start a new thread referencing the original post.