I think being able to have joint threads would be good for people who have training gyms
or are doing something with a mate

the real idea for what this should allow you to do, is to put someone else's trainer number or username in
And they can also edit the post (e.g rates for you're training gym change and you need to change them)

I've wanted to suggest this for a long time... Then forgot to. XD
I agree, it would be helpful, especially in training threads with multiple trainers.
10/10. :)