I envision a site where people could post their proofs -- either as answers to textbook exercises or revisions of current textbook proofs -- and get feedback on which parts might need improving, and perhaps how this might be done.
This sort of site could be useful to a number of people. Namely, it would be useful to 1) students looking to improve their proof-writing skills, or reinforce their understanding, and 2) those writing textbooks who want to try out their writing on the public.
This sort of thing doesn't seem quite right for the current math.SE and I don't know of any sites where it would fit.
My questions to you all are
a) Is this something that you have an interest in or that you think would be useful?
b) Can math.SE be used for these sort of questions? If not, is this sort of question appropriate for the SE format in general? Are there sites out there that do fit proof questions like this?
I know that codereview.SE fulfills this need to some degree for programming, but its scope is limited to best practices.