I keep a pseudo-bullet journal in markdown. Unfortunately, I rely on two things this (and a lot of other) Markdown editors won't do:

First, "-", "+" and "*" are all legal bullet characters for creating unordered lists.

This allows you to put further semantic meaning into your plaintext (for me that's notes, new tasks, events respectively) though it does get lost in render. This editor loses that distinction.

Second, and this one drives me nuts with MD editors not supporting it, "+<TAB>text" is just as legal as "+<SPACE>text" for Markdown--the spec, such that it exists, is just whitespace after the bullet.

I personally use that to create a bujo-style gutter column between the <UL> bullets and the text where I can insert a space and a resolution symbol without disturbing plaintext alignment.

So, "+<TAB>New Task" eventually becomes "+<SPACE>^<TAB>New Task" to indicate it's been tracked, for a final render of "o ^ New Task"

nvAlt is one of the few that does this right, and will actually copy the "+<TAB>" to the next line as a leader instead of only copying "+<SPACE>" or not treating the "+" as a bullet at all if a tab follows.

This editor won't even let you input a tab character. Tab always indents, whether it's opt-Tab, ctrl-Tab, or what.

I think Markdown is great, but the value I've seen is more in the semi-formatted plaintext representation than just being a text-based way to WYSIWYG. If I want WYSIWYG there are significantly more direct ways to get that. I wish more of the MD editors concentrated on optimizing the plaintext experience, as nvAlt is getting a bit long in the tooth.