> I agree that CodeMirrors general infrastructure for folding is more powerful than ACE's. But CodeMirror still lacks fold buttons on the gutter.
The folding utility in the distribution does lack them. But adding them (as in the 2.x code folder) is, again, just a few lines of code -- there's support for showing gutter widgets in the core, and the only reason the folding utility doesn't use that that I felt they didn't add much.
I'd argue that's not the case. The folding in CodeMirror v3 is on par with or even more powerful than ACE's.
> indent guides
If you mean the vertical rulers, they're not built into CM, but you can add one with a few lines of custom code.
> multiple selections
Should be coming to CM soon! https://groups.google.com/forum/?fromgroups=#!topic/CodeMirr...