As I read this question I noticed two comments by a user, consisting only of a link to php-pages on a site that did not seem in anyway related to the question.
I flagged them as
Other and stated why, but given the priority that spam flags are generally given, this seems like a loophole as the comments are still there one hour later.
Usually, this should not be a problem since commenting requires rep that spammers doesn't have. In the specific case, I'm thinking something is odd since I didn't get a rep tool-tip when hovering the username and couldn't click to go to a user page. So how could the user leave a comment to begin with?
EDIT: The comments have now been deleted, and AsheeshR's answer below is certainly valid. The pragmatic solution could perhaps be to update the "Rude or offensive"-option to "Rude, offensive or spam"?
Screenshot of the deleted comments: