Limit number of actual revisions

Looks like currently the revisions limit controls how many revisions will be kept and displayed (to those w/perm to view them).

How hard would it be to allow a limit on the number of times the comment may be revised? For example, an admin field for "max allowed revisions" and if I set it to 3, the fourth attempt just leaves the comment as is.
It could do this either by automatically "reverting" or maybe just by telling user "Max allowed revisions exceeded" and then reverting.

What I'm desperate for is some editing ability but only a little and I need anybody who uses the forum to be able to tell when an item has been revised.
(At the moment, I don't even know how to disable comment editing completely, which would have to be the plan B).

So if a feature addition isn't plausible, maybe a patch or a hack?
I don't have the PHP expertise to figure out how to get that behavior myself.