Right now when the user clicks the "Edit Keyword" button, a dialog pops up allowing to enter the keyword. Modal dialogs should be avoided when possible and there's certainly a better and more elegant alternative in this case. When the user clicks "Edit Keyword", the appropriate treecell should be focused and made editable, taking advantage of bug 201499.
My original implementation used editable treecells, but I switched over to the prompt due to accessibility concerns. Currently you can't invoke edit mode directly without a mouse (bug 350346) and they aren't read (by JAWS at least) when using a button to fiddle with startEditing(). I'll look into getting this to work properly.
Fixed by bug 1106559 (via bug 1106205).