I use rstrip routinely when editing idlelib files, before committing, so it has been useful for that purpose.

I do not happen to know what reindent.py does that the current format options do not.

#18704 was about integrating the pep8 style checker. That was closed in favor of adding a generic facility to run external analysis tools. There is not an open issue for that yet, but I expect it to happen, perhaps this summer. Reindent.py, if maybe improved, might be a candidate, though I will also try to look at the patch sometime.