In general we try to make our key bindings fit with the overall Emacs
style. We also have the following somewhat unusual convention of our
own: when entering a three-key sequence, the final key can be pressed
either with control or unmodified. For example, the
slime-describe-symbol command is bound to C-c C-d d, but
it also works to type C-c C-d C-d. We're simply binding both key
sequences because some people like to hold control for all three keys
and others don't, and with the two-key prefix we're not afraid of
running out of keys.
There is one exception to this rule, just to trip you up. We never bind C-h anywhere in a key sequence, so C-c C-d C-h doesn't do the same thing as C-c C-d h. This is because Emacs has a builtin default so that typing a prefix followed by C-h will display all bindings starting with that prefix, so C-c C-d C-h will actually list the bindings for all documentation commands. This feature is just a bit too useful to clobber!