I do not know if anybody has suggested this before, but would there be any usefulness in having a thread for commentary and criticism for those who like feedback to their work?

Don't you think people could just PM someone to give feedback?

I don't know, but it sounds like a weird thing to open a thread just for something like that. In the end I'd say its pointless after all, but that's just my opinion.

I am not the one who decides ^-^

Not sure if I completly understand what you have in mind?

Is it a thread for feedback on fiction, art etc, or a thread for feedback on RP styles, post and such?

It could be interesting, either way.

In the later case, I don't know how much useful input I would be able to give, personaly, being a relative newbie, but there are times when I do think I might benefit from the experience of more senior members.

I think it would fit in member creations. Just make a thread and post a couple of your roleplays for review and I'm sure members would be more than happy to offer you feedback!

I agree with Shai. If you want feedback put it in there. Opening a forum for general feedback on roleplay would be highly negative because it would encourage some people to critique the posting style of others without being asked.