Thoughts on this:

    module Foo

      def self.append_features(base)
        base.extend self
      end

      def foo
        # ...
      end

    end

I have done the above at times, as opposed to the alternative:

    module Foo

      def self.append_features(base)
        base.extend ClassMethods
      end

      module ClassMethods
        def foo
          # ...
        end
      end

    end

b/c I never liked having this non-descript module about --it feels
extraneous.

The downside of the former approach is that there is no way to ever
actually *include* the module's methods, but for the purposes of the
program that's almost certainly a YAGNI.

Any other downsides?