I think it would be nice if there was an option to 'privatize' comments made to images in the gallery. The option could be global, to be set by the artist who created the post, or local, to be set by the commenter.

Why? When I'm commenting, I feel like the others are ease-dropping on my comment, or that I am ease-dropping on their comments. Also, privacy can create intimacy which is an attractive and bonding force for the two participants.

The forum moderators should still be able to see all the comments during edit mode, but not otherwise.

if you wanna make a private comment you can always use site mail.

I always thought the comments were an instructional aspect of the site. So people could see what others thought of the image.

Yes I agree with Mark on tis one. You should site mail if you want to make a private comment to the artist. 

There is however a point to be made in reducing the embarrasment factor that critical comments can have .

if supportive and friendly, and if they include tips on how to improve the image, all would benefit from public viewing of said comments. of course, if said comments are entirely negative in nature, one can understand the desire to keep them secret, which is futile in any case.