Maybe there could be an option for the user to choose allowing or not allowing comments for pictures posted in the gallery. For those who want to post pictures but are not interested in comments/feedback (or at that point in their pottery where they want such feedback), comments would not be allowed/accepted. For those brave souls who are willing to subject themselves to comments -- objective or subjective, opinions, and the like, you could allow such comments to be posted.
Another approach is to let the user receive the comments first, then let the user decide whether or not to allow them to become public -- sort of giving the user the rights afforded the moderator for their gallery pictures.
Full disclosure: I removed my gallery pictures a few months ago; images of my work are on my website for folks to look at if they chose.