I don't like it, let say you read a thread "X" and then try to find him again and don't find him since he is called "Y" now. For me it would complicate forum navigation a lot, when thread owner change more then correcting their grammar.
The implementation should be quite easy, since GM and mod already can do it, but we do it just in very rare cases.
In case I am correct, the supporters have a bookmarking option for bookmarking a thread.
You can add to that an option for them to name the bookmark with
their name, and resolve this issue.
Yes, for those whe are not supporters it will cost more time to find the thread they are looking for.
BUT, this is not relevant or top priority - as the bookmarking issue (opened only for supporters) proves so.
In addition currently a user can delete or edit his messages.
Your argument could also be given about that.
This also proves that this feature is something that the BB developers may find worth the effort for users to then look for it.
How much does this feature is going to be used?
Not to nuch, and by that it is even less crucial for the case you brang.
So, if this feature is not going to be used frequent then why adding it?
Because it will still be used and it will assist where its coding's cost is very-low.
Is it a "top-priority" feature?
No. Not even close to that.
But, this folder is for all suggestions level.
Especially that this suggestion does not cost much, which mean that it may be decided to be added before a more critical feature that will take much longer.