> I *like* the CC size changes because the size indicates the indent depth.

My feeling is that you would be in a minority here.  IMO most new/novice users would find this surprising and confusing, since it is far from a customary UI experience.  Since our opinions obviously differ rather greatly on this, I suggest that we try to be objective and get some opinions from other users.

> The scrollbar slider bobble does not bother me much when scrolling with key or mouse wheel because I hardly see it.  My eyes are focused on the text.

On Windows, when scrolling with a mouse scroll wheel or a trackpad, I find that this makes scrolling rather inconsistent, since it will scroll more or less lines depending on the change in the number of context lines.

> Another possible solution is suppressing CC update at least while the mouse button is held down over the scrollbar.  Button down/up on the scrollbar instance sets text.pause_CC to True/False and CC update checks self.text.pauseCC.

I also see artifacts and scrollbar "jitter" when scrolling with a mouse wheel or trackpad, so IMO that wouldn't be a thorough enough solution.