I was thinking...
if the bumps without anything constructive to add do bother the moderators, then why not bring back the 'rate this thread' feature? and tell people that bumping is against forum policy.
allow the rate this thread feature to only be done once per thread by each person.
that way you would probably sort out the useful threads from the not so useful threads a bit easier.
they would no longer have mindless bumps, so the thread (in theory) should be full of input and additions. and those who agree that the thread should get some attention could rate the thread accordingly.
or those threads, which people think are just senseless can be given a bad rating?
well.. its a possibility anyway,
could remove the bumps but allow people to feel they have given their support to an idea and would encourage more actual discussion.
and since it is against the rules to bump then you may not feel so bad deleting any bumps that appaeared