Of the various insights into the diversity of Hogwarts culture JK Rowling has been sharing on Twitter lately, one in particular caught my eye. It wasn’t the revelation, reported by the Guardian, that the school had Jewish wizards. (So what?) Nor was it that Hogwarts probably had a few poofs in it. (We knew that already, didn’t we?)

No: what tickled me was her remark that the only group she never envisaged in the achingly multi-culti Hogwarts School of Witchcraft and Wizardry was Wiccans, those faux-druidic attention-seekers and drop-outs obsessed with black candles, lesbianism, and velvet gowns.

Harrowing news for lovers of Buffy the Vampire Slayer, to be sure. But smirk-inducing for the rest of us, who have been reading earnest, finger-wagging blog posts from self-described “witches” and “wizards” about how Wicca should be recognized as a “valid religion,” not to mention the risible annual nonsense played out at Stonehenge.

Wicca is religion’s answer to the Liberal Democrats, and indeed there is significant statistical overlap, and not just in sartorial matters such as open-toed sandals and hemp shopping bags, between the two constituencies. Invented by a retired civil servant called Gerald in the 1950s, Wicca has developed into a nebulous, splintered, egoist’s creed, where anything is true “if it’s true for you.”

In that respect, it’s a bit like Oprah’s book club, just with less cash and a fondness for tacky pentagram necklaces and about a tenth of the membership. (Depressingly, there are about 800,000 people in the world demented enough to describe themselves as Wiccans.)

Rowling expressed her disapproval diplomatically on Twitter: “It’s a different concept of magic to the one laid out in the books, so I don’t really see how they can co-exist,” she wrote. But what readers will have taken from her statement is surely: “Come off it, even by the standards of my totally invented fantasy-land full of mystical creatures, boy wizards, and horcruxes, those people are off their trolleys.”

You can tell quite a lot about those respective newspapers by which details with which they chose to lead their reports. The Guardian, with its creepy Jewish obsession, leapt on Rowling’s confirmation that Anthony Goldstein of Ravenclaw was semitic, while the Independent ran with her statement that “of course” Hogwarts would have been an LGBT-friendly place to learn how to magic-up enchanted water.

What neither of them saw fit to give due prominence to, though, was the fact that Wiccans, hilariously, are the only group in the Harry Potter universe incapable of performing magic. (Or, as they hilariously insist on spelling it, “magick.”) You’d need a heart of stone not to laugh.