This concerns MediaZilla itself. Users here should be able to edit their "own" comments. Sometimes a user may make a spelling mistake or may want to make his comment clearer, so, he should be able to edit his comment after committing it.
Version: unspecified
Severity: enhancement
Well, that could get confusing if people have already responded to the "broken" comment. So, it should only be possible for the last comment. But I for one would find a "preview" button more needfull.
Anyway, this would be a pretty heavy modification of Bugzilla, and should therefore probably be filed on http://www.bugzilla.org/