Earlier quoted context omitted.
> Just add a CSS stylesheet which turns into something half-decent, put a note that markdown is supported, and make a plain text editor. Any examples that you can think of which make a plain text area half-decent? So many sites go with heavy-JS options that i'm not sure what is possible for a good (half decent) visual editing experience in just CSS
Are you looking to avoid the js tooling ecosystem? As in, just an html file with script tags is fine?
Also, focusing on CSS first means - hopefully - that the UX is "as good as it gets" for JS-less individuals. If i add a small JS framework on-top of that it's likely fine.
edit: I'm sort of experimenting with how good i can make modern websites. Both on UX, accessibility, low bandwidth (folks on satellite connections appreciate this), etc. I'd like the site to "look like any modern site" (minus obtrusive crap), but suffer as few flaws as possible.