The question feed on Signal Processing is mostly comprised of questions bumped by the Community User, as discussed here on the site's meta. Seeing that Signal Processing isn't the smallest site in the network the same is happening at other sites as well. A solution could be to allow moderators to set Community's 'activeness', or have Meta.SE staff review various networks and see if the Community User is being excessively active.
Clearly abandoned questions: sometimes a question is neither good nor bad, and it's answerable, so it should be neither be closed nor downvoted, but there is an answer.
(a) Are we to upvote an answer for the sake of making bumps go away?
(b) Rigged incentive; sometimes we don't upvote because we don't understand the topic and cannot assess the quality of an answer. And reading questions and answers shouldn't be some chore one does just for the sake of making it go away.
The problem is worse than it may seem: for those on more popular sites, seeing several Community bumps on the question feed is no big deal - but on DSP.SE, these posts comprise nearly 50 percent of the question feed, on average. When you're a regular user, this isn't much better than ads being inserted between every other question.
"Just upvote an answer": 1(a), 1(b)
"Just downvote/close the question": 1. AFAIK, "OP's not here" isn't a criterion.
Lastly, remember that the request is to reduce, not eliminate, Community's activity. If we proportionally scaled up its activity for each network relative to DSP.SE, Stack Overflow would get 150 bumps every hour.