This looks pretty great. I've been frustrated trying to implement ACE in a project for Markdown support; it turned out to not work on iOS and Android at all, and it has a ton of bugs elsewhere, too. I ditched it for CodeMirror, which turned out to be nearly as bad on mobile.

A quick test shows that Monaco does work on iOS, although there's apparently no selection support within the editor. Surprisingly, double space produces "." as it should, but it seems iOS autocompletion doesn't work (not sure if it can be enabled).