I would think comment poster edit the comment to change collapse text could follow comment edit rules (yes, if they can ordinarily edit comments, unless the comment has been replied to) and if the journal owner has changed it, that should override the comment poster's settings. I have seen comment screening edit wars between LJ community maintainers and entry posters, and they are not pretty, so my vote goes in the direction of person-in-most-charge calling the shots. Comment creator/entry creator is still free to delete, of course.