[hoistbypetard]

The first thing I tried were checklists

    - [ ] foo
    - [ ] bar

It's my favorite thing about github style markdown. I doubt you need more ideas for your todo pile, but there's one for you.

[QML]

Another one would be to add support for LaTeX rendering :)

[amitmerchant]

I've implemented this in my app: http://www.amitmerchant.com/markdownify-web/

Additionally, it has a dark mode as well.