The lines removed here have been in Blender since way before 2.69. For instance it was in the Mar 23 2012 revision of editors/mesh/editmesh_utils.c in the EDBM_get_actSelection function. So I am worried that there is other code that depends on them. Will investigate further.

There appears to be some confusion as to how an active face is stored / retrieved, vs how active edges and vertices are stored / retrieved. The former sometimes involves looking at bm->act_face, while the latter always involves looking at the last element of the bm->selected list. Campbell, maybe you know the historical reason for this?

It makes it worrisome to make a change such as in this revision without knowing who is relying on the act_face method to set & retrieve the active face. Maybe this is OK, but I'm not sure. We don't have enough unit tests yet to feel safe about not breaking something else with this change. I propose an alternate fix to the problem in D664: Alternate Fix T40993: no active verts after extrusion.