I am narrowing the scope of this issue to Replace dialogs and widening the scope to output as well as edit windows. The attached patch solves the issue as redefined.  (It has a temporary hack to pass the unittests.)

For edit windows, the problem is that the default tag stacking order seems to be alphabetical.  No tag, 'builtin, 'comment', and 'definition, are followed and dominated by 'hit'; 'keyword' and 'string' come after and dominate 'hit'.  The solution is to raise 'hit' to the top.  The test (from msg225543), which should be added to htest), is that all 6 'i's in "def i(): this list is 'is' # is not" are both found and highlighted.  They are with the patch.

For output windows, the problem, mentioned in msg225382, is that the 'hit' tag is configured in ColorDelegator, which is not used in output windows.  Ths solution, also mentioned there, is to move the configuration to SearchDialogBase.  The path does this and Replace dialog Find work for Output Windows.

I tested on Windows.  I am 99.9% sure there should be no problem on other systems, but would like confirmation on other systems before or after committing an expanded patch with test changes added.