In an answer to a related question about vi-mode in bash, an answerer asked what would be next. Given that the operating system that shall not be named (the one that swaps constantly, even given 8 MB of ram) has been reported as being used as an editor and supports a plugin called evil featuring a vi-like input scheme, is it on-topic here?
I think that most, if not all, questions about evil should be asked at the Emacs.SE site. Not because I don't like Emacs, but because those questions will almost certainly get better answers there.
If you look over the questions, and especially the answers, then you will see that it requires Emacs expertise to give those answers, and not vi expertise. Do you know what these answers do? I certainly don't. I don't even understand the question, since it assumes you know what M-. does in Emacs.
After all, evil is really just a bunch of key mappings and commands built on top of Emacs.
This is why I put this restriction in my answer for 'What is considered to be vi?':
It must be a stand-alone program; so a plugin for Visual Studio that gives you vi-like keys doesn't count.
Because most, if not all, questions will be about the underlying platform (Visual studio, Emacs, and such), and will require expertise in that platform to answer.
This doesn't mean you can't ask questions if you're using evil. I have never used it, but I would suspect that many vi-questions on this site already work. But these questions are not really about evil, as such.
Let's see; does it meet the criteria we set earlier?
Its main purpose is a text-editor; anything other that has the vi user interface paradigm (as so far as one exists) is far too broad a scope. — Check.
It must be mostly compatible with the original vi for all basic operations; where mostly is not precisely defined. — Check.
So, yes, I don't see why evil shouldn't be on-topic.