Online comments system

Hi,
I'm part of the KDE documentation team, and we've recently discussed ways of
allowing users to more easily contribute to the KDE documentation. We're
interested in the comment system that you use on the PGSQL website, since it
provides a way for users to add to the documentation, with the potential to
merge the additions into the official doc later.

I'd be grateful if you could tell me your experiences with the comment system:
Do users contribute? Are the contributions useful? Is the system easy to
administer?

Also, is there some information online about the technical side of the system?
Is the source code available?

Thanks in advance,
Philip