Heads in hints are case-sensitive for special keys

[ShinyZero0]

For vim <esc>, <ESC> or <Esc> are the same key, but i just changed my head <Esc> to <esc> and got an error because it was still <Esc> in hint. That's unpleasant, maybe vim has a function to convert key sequence strings to some unified format so that they could be properly compared?