Whereas I found the fixed size to be much less usable.  The default of 3 lines was too few and often useless when context is needed whereas a realistic size of, say, 8, wasted too much space too much of the time.  I might prefer deleting the feature to reverting. 

It is probably a good thing to have 2 developers with different visual processing systems ;-).

With integral lines at the top of the text, scrolling one line down with a header line at the top means that the header line stays put while the background changes and the separator lines moves. A dedent line moves up as the context shrinks.  I *like* the CC size changes because the size indicates the indent depth.

Changing the general tab line from
  Max context lines:                              [ ]
to
  Code context lines:    min [ ]          max [ ]
strike me as an improvement even without adding min, and the somewhat obvious addition of min (it is currently fixed at 1) should not confuse 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.

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.