Nodes inside groups can't be muted
The mute operator explicitly disables muting inside groups. I guess this is a safety measure necessary for the old groups, where every internal socket is exposed directly and access to muted nodes from external links could break. Waiting for confirmation by Joshua before attempting to fix.
Bastien Montagne (mont29) has been working on a patch for a more general muting mechnism (see link). I will try to make a final review asap so this can get into trunk. After that can try to fix this one.