I'm the author of Markdown Here. And surprised to open HN and see it on the first page! I can answer any questions (although it's really a straightforward tool -- it does what it says on the box).
It suffers from a number of security issues [1] and it's unmaintained (or at least the maintainer is AWOL and without him new releases can't be tagged).
Markdown-it is probably a good alternative. [2]
[1]https://github.com/chjj/marked/issues?utf8=%E2%9C%93&q=is%3A...
[1]: https://github.com/adam-p/markdown-here/tree/markdown-it
# DO NOT ET CETERA
...And then render.
It looks pretty!
It's not super high priority, but someday...