Hey Brynn,
Given that Martin hadn't responded that I could see, I'm going based on the information that you provided.
I do not believe that moderators should have the ability to modify the content of a user's gallery post or their description. However, given your stated concern and rationale, the ability to disable hyperlinks needs to be a way to balance that as a reasonable form of moderation. IMHO, there should be a moderation flag to disable hyperlinks in all text URLs in the description via 1-click (force the entire description into plaintext if need be). It may seem overbearing to disable all hyperlinks in a description if one is spam, but realistically, if we have clear guidelines on what is considered spam, it shouldn't be a problem... plus a plaintext copy of the URLs will still be right there, so what they posted is unadulterated, just no magic hyperlink is created server-side.
Does that seem like it could be a reasonable solution? If anything, it seems like it might make it quicker/easier to moderate with a single-click rather than having to edit content. I'd be interested in people's thoughts.
Cheers,
Josh