Dealing with erroneous "many" counts

I have a spamtrap set up that automatically does a -tmany on mail that
hits spam-only addresses.  It works fine, but now and then I fat-finger
something and mistag something that I shouldn't have.

Is there any way to undo a mistake beyond adding it to my local whitelist?

More generally, is there anything in DCC to defend against users or leaf
nodes who are overenthusiastic or malicious in their tagging?  I realize
the straightforward approach is not to let people who do that participate,
but if I use this for a lot of mail, it's gotta be entirely or mostly
automatic.

Regards,
John Levine, johnl@iecc.com, Primary Perpetrator of "The Internet for Dummies",
Information Superhighwayman wanna-be, http://iecc.com/johnl, Sewer Commissioner
"I dropped the toothpaste", said Tom, crestfallenly.