Hi,
while playing with the Measure_grouping_engraver
see:
http://lilypond.1069038.n5.nabble.com/changing-symbols-used-by-Measure-grouping-engraver-td215283.html
I noticed two things which may qualify as bugs.
(1) A documentation issue
I tried to get MeasureGrouping in default 4/4-time, but nothing happened.
One has to set beatStructure and baseMoment accordingly. The current
docs make it sound it should work out of the box, though.
\version "2.19.82"
\new Staff \with { \consists "Measure_grouping_engraver" }
{
%% to get MeasureGrouping, next two lines need to be uncommented
%\set Timing.beatStructure = 4,4
%\set Score.baseMoment = #(ly:make-moment 1/8)
\repeat unfold 8 a'8
}