Since approx. August 30-31 VisualEditor breaks when Polish-language diacritics (ążśźęćńółĄŻŚŹĘĆŃÓŁ) are input. The characters themselves disappear and text around them gets mangled and moved around.
They're all input using AltGr (right Alt) + diacritic-less version of the characters, with the exception of "x" mapping to "ź" (so, respectively, azsxecnol).
I have been unable to replicate the issue myself, but it's definitely happening.
This is repeatedly breaking page text on the Polish Wikipedia, so I'm marking the bug "highest critical".