I think it's an issue. I have created quite a few threads that upon submitting thought better of it and deleted them. If you had a problem with my Edward the Vampire and his allergies thread, you would have really hated my others. Which is why I need a personal board.
The time limit for editing the thread title is currently 5 minutes. What do you think it should be? (Apparently infinity is not an option.)
I couldn't find a separate setting for deleting the first post in a thread. Either (a) you are incorrect, and the first post can indeed be deleted, (b) it uses the same setting for editing the thread title for this, (c) there is no setting; you just cannot delete the first post in a thread, or (d) something else. My working theory is (a), since I just tried creating a test thread and was able to delete the first post in it (which caused the whole thread to be deleted, incidentally). However, I'm an administrator so perhaps I have more permission for things like that. At any rate, there doesn't seem to be anything I can do about the global settings in this regard.