I'm sure you know what you mean by the difference between Markdown "flavors" (bad, don't need) and Markdown renderers that let you pick and choose different extensions (good, more of that please).
A flavor is a slightly different syntax, a renderer is the software that outputs format x from markdown. So flavor A can only be rendered by renderer A, but vanilla markdown can be rendered by all renderers. Different renderers can produce different output based on the options you give them, though
Sure, and Markdeep handles vanilla Markdown just fine. It also offers some extensions, which can't be standard by definition. I don't see a problem with that, and I definitely don't understand the distinction the grandparent was trying to make.
But, I don't.