I have done a thread prefix on this post.
If you click on it in forum that has lots of prefixes it will show you all threads with that prefix.It's very green.
What does it do?
Yes we'll need to think about how and where they might be useful (and how and where they might very much not be!) but it's something to keep in mind I suppose! Could start to look quite chaotic with them everywhere but you can see how it might be nice in eg Charts, Rates etc.Might be handy if we use these to add prefixes for album threads/single threads/tour threads/general discussion. Makes filtering so much easier.
I believe some forums who utilize prefixes also have them vary by color so that it's easier to spot what kind of threads are which. Almost like a flair for a thread's title.Have you considered perhaps making it pink?
One possible usage is to use one for spoilers for TV so it's easier to find threads where spoiler discussions is allowed. Maybe prefixes for RPDR and Real Housewives as opposed to the requests for their own separate subforums.
For Charts & Rates, types of threads can be utilized to designate which threads are Rates vs not.