Have not read the whole thread but the first few pages.
This idea sounds very good so far.

One thing I want to mention is that it speeds up analysis if the artists leave some words on what
they noticed, what they think doesn't fit and what is done intentionally.

If for example someone has done some weird lighting/shadow in a pic and knows about this
issue, but doesn't know how to fix the problem, then it would be useful to know for the
commenter. If it's intentionally weird it's also good to know...
Otherwise it's always a lot of consideration from what the artist might be aware of, what he
won't change, what he can't change to what's his goal for this pic.

Regarding new users, a knowledgebase could turn to be an great addition.
I don't know about the Poser Manual too well, but the manuals that come with XSI, shade and
maya are not really that much of a help if one needs a quick solution for some specific problem.

For Poser the most obvious problem, if looking in some random galleries, seems to be that
people simply have no idea how to rig the figure. Next thing would be how to use lights. (This
"standing in front of nuclear blast lighting" syndrome)
There are for sure more things like these that can only hardly be explained within a few lines of
comment.

Now it's more than 1 thing but well... :p

My 2c
-tow