Don't care on dotted access.

Context addressing is fine if we can agree on a method and keep the spec simple. Perhaps using Git's SHA addressing with things like HEAD, HEAD^, HEAD^^ or similar.

Yes to booting dynamically changing delimiters.

Yes to stealing helpers.

For cross-language compatibility, we really should have a collection of test inputs and outputs.

We should adopt a directive thing like you have for the 'this' notation with {{.}} or whatever for lists. The original is a bit funny looking but I think this sort of thing would fix the delimiter issue.

Another pattern that I run into that's a bit weird is when I need to add markup around a list when its not empty. I end up having a context that returns a context with a rows object when there is data, or None when there are no rows. So it looks like this in mustache:

{{#genes}} open table {{#rows}} row stuff {{/rows}} end table {{/genes}}

I keep having the feeling there's a better way to make that work.

If I get another project finished up shortly I'll write these up in a branch of pystache.