t.co/eqdwe7Cqu1?amp=1
'signed anonymously from a number of trade figures, including publishers, writers, illustrators and booksellers' - no editors, though, judging by the rambling, over-long text. It seems to be in part a response to the evidence given to Parliament last week by the CEO of Hachette, who are JKR's publishers, about cancel culture. JKR not namechecked but I bet they had her in mind.
Some fairly robust responses on Twitter, I see.