That's the solution. For instance, if you've got text that's bold and you didn't want it bold that means there's an extra [b] in there somewhere. If you find it and delete it that should take care of it.
You can also sometimes play with deleting spaces, backspacing, etc. But that can be a bit of a guessing game.
My biggest complaint about the editor is that it's WYSIWYG yet this extraneous formatting doesn't show up in the WYSIWYG view -- that makes no sense. It's annoying to not see it until the listing is previewed.