I know that some people have complained about not being to map multibutton gaming mice. I can see that is a nice to have feature, but I would suggest that getting keyboards working properly should be a higher priority.
Some common keys are showing up as "Unknown" in the key map interface.
TAB - Unknown
DELETE - Unknown
BACKSPACE - Unknown
I am sure there are many more. I suspect the numeric keypad falls into this list. I don't have a keyboard with separate num keys to test, but I'm seeing a lot of "Unknown" maps in the right hand column, which I seem to recall were num keys.
While they each say "Unknown" they do retain their identity in that mapping TAB does not cause a conflict with DELETE. It just becomes very difficult to determine what your key maps actually are.
Also worth noting, the UI map enabled keys do not honour alternative OS level keyboard settings. Specifically if your system is set to DVORAK or COLEMAK, you need to use the QWERTY key positions for mapped keys. On second look, the default key map uses the position of the QWERTY key, but the current keyname - so the default Inventory key on a Colemak system is "U" which is where "I" is located on a conventional keyboard.
Fortunately, the chat interface does not share this problem, so it is fairly easy to just in and remap the UI key settings without having to change back to QWERTY just to play a game.