Der Deppenapostroph

From The Guardian, “Germans decry influence of English as ‘idiot’s apostrophe’ gets official approval”:

A relaxation of official rules around the correct use of apostrophes in German has not only irritated grammar sticklers but triggered existential fears around the pervasive influence of English.

Establishments that feature their owners’ names, with signs like “Rosi’s Bar” or “Kati’s Kiosk” are a common sight around German towns and cities, but strictly speaking they are wrong: unlike English, German does not traditionally use apostrophes to indicate the genitive case or possession....

However, guidelines issued by the body regulating the use of Standard High German orthography have clarified that the use of the punctuation mark colloquially known as the Deppenapostroph (“idiot’s apostrophe”) has become so widespread that it is permissible – as long as it separates the genitive ‘s’ within a proper name.

The article notes that a spelling guide used in schools and public institutions gives “Eva’s Blumenladen” (Eva’s Flower Shop) and “Peter’s Taverne” (Peter’s Tavern) as acceptable spellings but proscribes “Eva’s Brille” (“Eva’s glasses”). Because Brille is plural?

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October 12: There’s now an explanation in the comments that seems right: “Eva’s Blumenladen” is a proper noun, the name of a particular shop, but “Eva’s Brille” isn’t. Thanks to Cassidy Napoli for bringing things into focus.

[And it has to be said: the apostrophe is not a matter of grammar. I agree with Geoffrey Pullum that it’s not even a matter of punctuation. It’s a matter of spelling.]