[WetWired]

Currently there is not, though obviously a banned member's activity will fall.

I assume that this is an automated news poster you're trying to deal with? If it always posts in the same forum, you can make posts in that forum not count to reduce activity level.

I suppose it would be easy enough to add some sort of usergroup check, though it would disturb the optimizations that prevent checking everyone's activity each day for the list.