Is there any kind of consensus emerging yet as to what regions and genres this is specific to?

I understand the lifted foot signal, but I'd say I've only experienced it with Old Timey musicians in America (and maybe with the Irish dance tunes, sure, but as played by Americans whose repertoire blends that and Old Time seamlessly).

As for me, I'd usually just shout out "YO!" during the last chorus, to wake everyone up!