version: 2.77 (sub 0), branch: master, commit date: 2016-03-16 00:33, hash: bd5bfad, type:
I am sorry to report this here since it is not strictly a bug (however I was unable to find another appropriate place to post this, despite of the "developer contact page").
When using the grease pencil and having a dope sheet for the grease pencil open, new keyframes will be inserted if the eraser is activated. By this I mean if holding D and pressing RMB. The keyframe will be inserted regardless even if no data was erased. The behaviour is the same when holding E and pressing LMB (with Enable Editing).
It would be good if a keyframe would be inserted, but only if data was actually modified. Furthermore it would be perfect if the keyframe was only inserted for the layer in which data was modified (currently it is inserted for all keyframes). With the current behaviour, the dope sheet can get cluttered very easily (and currently in the dope sheet for grease pencils you cannot say if a key is different from a previous key, which makes things even more cluttered).
Despite this report (and my bug reports which have been fixed immediately - thanks!) I wanted to point out that working with the Grease Pencil is easy, quick and just great.