I've seen this as well only starting with Xenial. Due to other Cyrillic bugs, I wasn't using Ubuntu fonts as my default font family in Wily, so maybe I missed this change and it was there as well, but this is definitely broken in "Ubuntu Sans Bold" in Xenial.
I don't see the problem in any other Ubuntu font (Mono, Condensed or Sans).
I've seen this as well only starting with Xenial. Due to other Cyrillic bugs, I wasn't using Ubuntu fonts as my default font family in Wily, so maybe I missed this change and it was there as well, but this is definitely broken in "Ubuntu Sans Bold" in Xenial.
I don't see the problem in any other Ubuntu font (Mono, Condensed or Sans).