But English is not the largest language in terms of the number of speakers. I speak Korean for example and three-digit grouping is unnatural in Korean, which uses myriads instead. I guess Xenon is designed to be not comfortable for the vast majority of people including me then?

> Having special names, like $type, and hoping no language uses them is fragile.

I was not proposing special names after all. Xenon clearly has a much better extension point, namely the type string. You can have just one reserved character, which is very unlikely to appear in verbatim, and use it for the extension. And it is even unclear whether JSON's use of `$` for such special names was fragile after all, given that such complaint seems uncommon. (I complained about that in the past, but I mean others seemed to be cool.)

In addition, I don't think you have mapped enough languages to conclude so anyway. For example, can you list all popular enough languages that allow `$` in identifiers? While whether to allow `$` or not requires a single example, maybe you have missed other identifiers in other languages! (Angle brackets are also common in stringified types, after all.) So I expected you to have at least looked at them for your conclusion.