Earlier quoted context omitted.
Shouldn't shift be twice as hot as the parentheses?
No because this heat map is clearly generated "offline". That is, this is built from a source-file dataset. An "online" dataset would be the output of a key logger. Online analysis would show the number of right parentheses to be a tiny fraction of left parentheses due to auto insertion and other paredit-like operations.
And furthermore, where are all the numbers, tabs and spaces?