[hsivonen]

Notably, the single menu item in Firefox does what it says on this page, so this page doesn't demonstrate why having just one menu item is a problem.

[int_19h]

I'm sure it works quite well with UTF-8. I'm less sure that it is able to consistently distinguish e.g. various Cyrillic encodings. And yes, CP1251 and even KOI8-R are still occasionally a thing when it comes to websites.

[hsivonen]

Have you encountered concrete cases of failures with Cyrillic single-byte encodings (where the letters fail; there are cases where box drawing characters fail due to preferring letters over box drawing)?