The complaint about Standard Markdown was that it appeared to be hijacking the existing "brand" in order to present itself as the definitive version.
One definition of "Common" means prevalent and it seems to me that this word was picked not to solve the above problem but to get around it by making Gruber look like a dick for objecting again to the same problem.
Ironically, a second definition of "common" is "showing a lack of taste."
Or, alternatively, the largest sites that all use Markdown wanted to figure out how to build a Common Markdown format that they could all agree on (or Standardize on), since the original hadn't been touched in a decade.
Yes, the License does say that derivative works shouldn't use the Markdown name. And yes, I'll even agree that it's a somewhat classless move, assuming you ignore years of context. "Github Flavored Markdown" is a thing, has been for a very long time. Not a peep from Gruber about it. It is highly reasonable to expect that "Common Markdown" (or even "Standard Markdown") might not raise any hackles.
C'mon, you really think folks are sitting around, plotting the best way to steal John Gruber's one serious project?
In the podcast John Gruber did with Marco Arment ( https://overcast.fm/podcasts/episode/344902019595#t=4527 ), John Gruber notes "Github Flavoured Markdown" is a good product name.
He also says that they should standardise using a different name.
Nonetheless, a tiny percentage of reddit users who know how to use the formatting still likely represents a majority of the set of people who know about Markdown formatting.
> Ironically, a second definition of "common" is "showing a lack of taste."