The initial post should be a comment period where you ask for feedback and no matter how large your mistake, it should be considered okay.
And slowly as you get more eyes on it, it should solidify into a more accepted paper.
Today's system is already collaborative. It is precisely those people with the expertise, interest, time and funding in a particular problem that co-author the papers. Then there is the review process to provide feedback and spot the serious mistakes and problems with the papers. After which, for significant works, there are follow up papers by various authors to expand, refute or clarify the original work.
In fact, that makes ego validation easier: "I contributed these insights, reviewed these contributions, and received these upvotes/contribution acceptances."
Of course you can see the contributions in the VCS history, but that doesn't translate to public recognition.
It's not like scientists are in it for the money...
Have you seen papers in particle physics? Sometimes they don't fit on a single page!
Lijie Chen (the student Scott mentioned) used arXiv.org's preprints for this purpose.
Right now, there are websites which allow people to discuss papers, but the problem is that a paper has no "home", so the discussion takes place on different sites, and therefore gets watered down. I guess we need to agree on a standard.