Is less(1) missing lesskey functionality?
The Lion build of less indeed comes with the lesskey feature disabled, as can be seen by the customized defines.h it is being built with (line #define USERFILE 0). This doesn't mean it's broken, just that someone decided to customize the build and disable this feature for whatever reason. Sadly they neglected to update the man page, which is why it's still referring to it.

If you want this feature, building your own less from source is just a matter of ./configure &amp;&amp; make install (which puts it into /usr/local), and you might also want to get a more recent version while you're at it.