Two things come to mind in response to your post. The first is mute. By muting spammers, those comments no longer impact your attention. This, however, may preclude the spammers learning from their mistakes, and, should they transition to commenting substantively, might negatively reinforce that evolution.
The second is adding a simple dropdown menu to the flagging option, that has some few tags: spam, pr0n, etc., that would allow curiosity to be satisfied by folks without having to reveal the flagged comment.
Thanks for your lucid consideration of this topic!