Last modified: 2013-02-18 13:22:11 UTC
Since Bug 24704 did get closed without addressing the problems (wtf?!)... Here it is: it is not clear that there should only be entered one category in the field. In fact the heading over it says "Kategorien" (categories) but only one field is visible. I saw one entering a comma-separated list in there... Put a bullet (<ul>) or something in front of the cat fields to show that this is a vertical list of cats.
There's a link below the button saying "Add another category", autocompletion of the category name, and an indicator "This category will be created" when you type the name of a category that doesn't exist. All these are subtle affordances that you're dealing with an atomic category addition. It's possible that it's still confusing, but I'm not convinced it's a significant issue. Please point to examples of users being confused by it (if other users experience the current UI as confusing, please point it out here).
I cannot give you examples (also due to the fact that I am not anymore active at Commons). I think I saw once some anyhow.
I agree with Erik. Also adding bullets isn't going to make it any better
