The best tool for writing documentation is the one that you enjoy using. Most documentation is crap, and it's really not that hard to port one markup to another

The best tool for writing documentation is the one that you enjoy using. Most documentation is crap, and it's really not that hard to port one markup to another (it's an hour or two of pain, but that's it). I've tried restructured text, and it's just slightly painful enough that I drag my feet writing docs in it. I haven't tried the other suggestions, so I can't comment on them. The nice thing about markdown is that it's "good enough" and ubiquitous. My READMEs and static websites are in markdown, and many tools have markdown-style options. Even Reddit uses markdown, which is pretty neat. Yes, the "flavors" are mildly annoying, but they're close enough that it doesn't matter too much. I don't love markdown or anything, by it is "good enough", so I haven't bothered trying to replace it.