[hos]

members can only change the thread title as long as they edit their first post and no other member has visited it yet. as soon as it was visited, thanked or answered he can just modify the post title without any effect on the thread title. these titles are 2 different items in the database.

the moderator can always modify post and/or thread titles. if a modification of thread or post title affects the other item as well, depends on which edit-dialog he is using. he can modify them both with one action, or each item separate. i assume, most mods don't know much about the technical parts of the board software, they are editors, but no software/database experts, so you will see those thread/post title difference quite often.