You can indeed use plain markdown and get all the features you are thinking of. You can color with html, since you could add that to markdown and support it reasonably well. Performance takes some thinking but is not a major issue. This also simplifies versioning, since you could e.g. just use git. I've been working on a notes app that does these things -- not ready yet, but these are all doable. Comments like these remind me its worthwhile (beyond my personal use).