Great news! When can I expect it to come to the release channel? Or which Safari version will have it? I'm looking at the release notes but I have no idea how are these being merged into normal release.

That would work only in Safari, not in Chrome / Firefox where it would print two dollars. The docs you are referring applies only for "named substitutions", not index substitution - which is what I use here. It's just another broken API :(. I can't believe that Apple which makes awesome future-like hardware makes such a buggy software. Also this is a regression.

So you were able to reproduce the problem? Yes I ended up escaping the dollar character with another dollar.