I think such a feature would just be too tempting to abuse, for whomever has such an ability. It's already annoying enough when people vote in a poll, essentially reviving the thread, without providing any more discussion on the subject. I don't see that as an "advantage," but rather a nuisance.
Now think of such a situation with a bunch of threads mysteriously at the top of the pile, with no new material. The only reason they're there would be because someone thought they needed more discussion, but were too lazy to provide any input of their own? If you think a thread needs bumping, come up with something interesting to say to jumpstart the conversation again.
We already have a "bump" button, it's called "post reply."