It used the "Rich Text editor" version of update.bml, and then saved that as my default without asking me. Bastards.
Deleting the post, loging out, deleting cookies, using another browser on another computer, nothing made the bleeding-awful grossly dysfunctional, untidy, dirty, ugly Rich Text Editor go away -- unless I logged in as a different user. I don't particularly want to delete this account.
FAQ 204 says "if you post an entry using the Rich Text editor, the Edit Journal Entry page will display your entry using the Rich Text editor. There is no way to switch back to the ordinary editor once you have done this". Idiots.
If LJ have condemned you to using the Rich Text editor version of update.bml, don't despair. There are options other than deleting your account and moving over to myspace.
There's a couple of undocumented pages which allow you to change the default back again.
Welcome back, sanity. Come in, sit down.