Such a document would be a great starting point for many newcomers to the Emacs community and should increase the overall quality of the code produced by it. There’s much to be documented about code layout, preferred syntactic conventions, major and minor mode definitions, etc. and I obviously can’t know the best practices about everything so I’ll need a lot of help.
Of course, we already have the official coding guidelines, but they are a bit light on examples, rationale, etc. Hopefully the community style guide will manage to fill any gaps in them and in good time portions of it will find their place in the official documentation.
I’m inviting all members of our community interested in promoting good Emacs Lisp practices to join the development of this document!