Hi Andy,
You tend to get 3 types of users:
1) People who use the gallery to store their photo's and hope to get ratings
2) People who use the forum and upload photo's so they can be discussed in the forum
3) People who do both 1) & 2).
There have been many debates about the value of comments in the gallery and there are many viewpoints, but basically with so many images loaded per day it's impossible to comment on them all and maybe people who are looking for comments should be the ones providing them for others
If you want feedback or opinions on a photo (good or bad - but honest) then the best advice (for this website) is to add them to the photo critique section, or one of the specialist sections. You normally get people who will comment then.
Phil