Personally, as an admin, I find bump posts to be distracting. When I first log on, I go to "all unread posts" and scan down the list of last posts on the far right. As soon as I see a post by a member whose name I don't recognize, I zoom in on it. Most often it's a spammer. So I get busy with the banning/deleting posts job. I usually ban the bad guy and then list his posts on a single page and delete them one by one.
But if the post has been bumped, then it takes me longer to find the spammer. I assume there is nothing wrong and proceed to go through all the new posts in an orderly manner. Sometimes I don't get through all the new posts in a single sitting so the spammer could stay hidden until the next time I or another admin/mod reads that topic. The reason the spammer's post stays hidden is that the bump post appears as the last new post on that topic. The spammer's post no longer the last new post on the topic, because the bump post has hidden it.
Also, once I have already deleted the spammers posts, I still have to go to all of the topics that have been bumped to read any new posts. Those topics show up with new posts in them. Reading topic after topic with "bump" posts only as the new posts takes additional time as well. Remember that we admins/mods try to read every single post.
So for me, as an admin, it's better not to bump, but to click on that "report to moderator" button. That's always a good heads up for us.
I don't know how the other admins/mod feel about bumping, but as I said, for me, it makes sleuthing out the bad guys a bit more time consuming.
I appreciate the efforts of our members to help out with bumping posts, your hearts are in the right place, that's for sure

. But personally, I'd rather have a "report to mod" notice.
And finally, just because a spammer has posted on a topic shouldn't stop anyone from posting on that topic after the spammer if they have something to say about the topic, ignoring the spammer of course.
Thanks,
Kathryn