I realized after posting that looking for close matching is a performance issue and does not need to be done unless the exception is going to be displayed.  But it is a shame to keep such great work away from many users.

What would you think of either

1. add sys.tracebackhook, to be called by the traceback display functions if not None.  Then idlelib.run.print_exception would not have to duplicate the sometimes changing logic for chaining or otherwise joining multiple tracebacks into one mega-traceback.  Instead, from what Dennis said above, it could set the hook and call the built-in exceptionhook.

2. add a new optional parameter to exceptionhook and the traceback display function.  This would have the same advantage as above.