> So not changing a spec for over a decade

The problem was there was no _specification_. It was a 'how to use' summary, And each implementation could be (and was) different in subtle edge cases.

The point of CommonMark was to define the specification and stick to it.

I agree with GP, I thought it rather sucky that he objected to using the name.

Various markdowns have extension mechanisms, they always have. That's not what the GP was talking about.