You can activate or deactivate comments easily by going to "Customize" >> "Site Settings" >> "Functionality". Also you can activate or deactivate comments individually for each album by going to "Tools" >> "Album Settings" >> "Functionality".
What about flooding & spam? The unregistered users are required to recognize and pick a set of pictures in case they want to comment. It is an implementation of a spam protection system consisting of CAPTCHA images.
Comment management pages. The owner of a photograph may remove associated comments at any time but this action cannot be undone. You may review all of the comments you have ever received by going to "Visitors" >> "Comments" , and all of the comments you have ever posted by clicking the "See Sent Comments" link on the same page.
You can get an e-mail when you receive a comment. If you wish to be always informed of any new comments, you can set up e-mail notifications by going to "(your login)" >> "My Account" > "email settings".
What can I do next? You can check your photo liking settings.