There’s an “or” in that sentence: “old or unsupported browser”

Nitpicking cool projects is also pretty disparaging.

Sorry if I hurt any browser's sensibility. Hope no browser was offended by my app :)

However, I didn't refer to "browsers that don't follow an early adopter in implementing a working draft" as "old", though; if you read the compatibility message carefully, you'll find I referred to them as "unsupported" (which might be a bit inexact but not disparaging).

Non-evergreen browsers, instead, are correctly referred to as "old", because they are.

I guess so. But then again, there's a bunch of people who are taking care of the draft and browser vendors will probably implement it soon. In the ever changing world of web development, that's as close to a standard as you get, if you don't want to wait years. But yep, technically it's a W3C draft, which might change and which I'm actively monitoring.