deleting an entry isn't complicated (unless you're viewing it in notepad with word-wrap on, in which case it becomes kind of a simulated hex-editor experience...); you just remove one block, along with ONE (1) of the full-stop (.) characters above and/or below it. that seems to work fine.
i've never tried altering the contents beyond deleting a block... the login information gets encrypted in a way that's effective at keeping you from working with it, but is probably much too weak to actually keep someone who really wanted to crack it from doing so... oh well.