Seems to do exactly what it promises to. What I would personally really hope for in a filter add-on like this would be the option to filter *out* certain content, however.
I understand that getting people to actually report/block spammers is important too, but for that reason too, I feel it would be useful to at least have the instances of the same message spammed at least reduced to a single, perhaps highlighted item with a single button to block and report at once, rather than letting them show up just as intrusive as in the regular chat.

Very useful. Wish I could import/export profiles, and add multiple authors at a time.