You have the same behaviour every time you touch the bug in other ways, for instance adding a note, which is exactly like a bump.
so do you propose to add a config option also for that?

Well, notes are different. Probably I gave bad example. Better one would be following a topic in forum. Nobody really cares about that.
And, by the way, you usually can't comment on a closed report, though you can monitor it.

Why would you want to monitor a closed report?

In fact - I think i'd probably consider that to be a bug. In theory, CLOSE'd is the last state that a bug will enter and unless it is reopened ( i assume quite unlikely normally), you'd be monitoring something that will never change...

Bump! --- I think it is useful to get a bump when someone monitors an issue, this is because there is interest in this issue and it is worth surfacing to the top. However, I wonder if it is worth the bump if someone unmonitor the issue (except for consistency).

On the other hand, I wonder what you see as the disadvantage of this ON? Is there a certain behavior that causes this to be perceived as a negative thing in your environment?

Hi,
I'm a bug moderator on a Mantis BTS myself. I usually browse bugs everyday to see if something was changed. Frequently reporters monitor issues, so I have to check every of these issues because last updated time has been changed. So it takes my time for unnecessary opening such issues.

And here is an example when a user monitors closed report: http://bugs.miranda-im.org/view.php?id=59

Thank you for bumping this report :)