The link doesn't give any examples of the extended featureset, but there's some neat stuff here:

https://github.com/ttscoff/apex/wiki/Syntax

github repo (MIT license): https://github.com/ttscoff/apex

I heart ttscoff. But I'll still wager that this is the latest rabbit hole that explains why nvUltra is still not released.

You’d be incorrect.

Why would I use this over pandoc?

This question is always annoying, but I'll bite:

1. Because Apex processes more flavors of Markdown and seems to have more configurability with regard to Markdown syntaxes.

This is not a knock on pandoc. I love pandoc. I use pandoc every single week day.

2. There is no obligation for you to use it. People can create whatever they want and share it with whomever they want.

The question was asked in good faith, not as a set up for an argument. I'm sorry you feel put upon or need to become defensive about a honest question...

That first sentence I believe. The second not so much.

Inevitable:

https://xkcd.com/927/