Not really a bug, but confusing interface things are in my opinion worse than bugs.

The interface towards the bottom of most pages, that leads off “I want to” and has a button that says to add it to your list, looks a lot like a search interface. Yeah, so it’s clearly labelled, but people don’t actually read everything they click on. I entered some stupid thing there, let’s say “suck less” and all of a sudden I have a goal that’s entitled “suck less”, without going through any confirmation interface or anything. Meanwhile, when dropping that goal to “suck less”, I’m given the 5th degree – an extra screen devoted to scaring me with how I’ll never ever get to “suck less” again, any entries I’ve ever written about “suck less” will be gone, etc.