For 3.x, I think 7.7 Class Definitions should mention the metaclass
keyword arg and cross-reference 3.3.3 Customizing class creation. Since
it is no longer a 'special' name, let alone a 'special method name',
there is no reason to know to look for it under that heading (I didn't
until I looked for 'metaclass' in the index, which I had to know to look
for, of course).

A possible sentence after "The class name is bound to this class object
in the original local namespace." (and before discussion of @classdeco)

"To modify this process, add 'metaclass = xxx' to the list of bases and
see CCustomizing class creation." with the last three words being a blue
link to 3.3.3.

2.x would need something a bit different, or just less ;-)

Should be fixed in r83538.