>>903751 (OP)
> So are there any actually good markdown editors, or should I just learn Vim?
Why do you even need a Markdown editor? It's just regular plain text. And yes, you should learn Vim (actually Neovim), then you'll have a text editor that can be used for any language, not just Markdown. If you want live previews there is probably a plugin that render the HTML in a browser and refreshes the page.
>>903768
LaTeX fails at being a 100% semantic format. Even something simple as ending a sentence with a math formula requires you to concerned youself with presentation. Additionally, LaTeX is intended for print or PDF, if you want to convert your document to HTML or some other format it gets messy. Markdown is good for being a high-level markup format that can be converted to lower-level documents. (reStructuredText is still better at that though)