Thanks for this information, Brian. I'm researching this "substantial improvement" stuff so as not to violate the rule against duplication. Your is the first article on the subject that I've found after reading Medium help and not finding anything specific enough. I might write something on the subject myself, if I find out enough to warrant doing so.

By the way, I'd like to follow you but cannot. I have a help ticket into customer support for that--help buttons disappeared a few days ago on pages displayed to me--but if you want to follow me, I can still find a follow button in announcements of new followers