Placed between "Update issue" and "Cancel" now, more logical position for a secondary button, but I'm concerned that people will make changes to the issue, and then press "Bump!" expecting the issue to get updated and bumped. Or no, that's just me being paranoid, people using Bitbucket should have enough technical experience to know the difference :)
I understood what "Bump!" button does only after I read Thomas Waldmann's comment. I agree with him this button should come with a hint or something to clarify what it does.
Also how many times can you bump an issue, and who can you know if it's bumped or not?
It would be nice to use some ajax on the button so that it doesn't refresh the page and jump to the top of the page. This will also solve the problem that if my comment was updated by pressing the bump button or not.