> AFAICT, the recommendation to use hg "git" format is currently only mentioned in the Committing section (http://docs.python.org/devguide/committing.html#minimal-configuration) but not elsewhere, in particular, not http://docs.python.org/devguide/patch.html.

Good observation.  Personally, I think it makes sense to keep Mercurial information for both committers and non-committers (like configuring to use the "git" format) outside of the Mercurial section specific to committers.  This can be in a general Mercurial section before the section specific to committers, or else spread throughout (e.g. in the FAQ).