Can you elaborate on this? I've had much more benign experiences with self-described radical feminists than a lot of people in my life seem to have had, and I'm wondering if it's maybe a particularly toxic milieu in Britain, or among relatively-older people, or among straight women, etc.
In a British context it would refer to a very particular loose network of people dating from the 1970s and for a long time based around a couple of low-circulation magazines and periodicals, and now largely on social media. We really are not talking of many people at all,
but they have always been greatly over-represented in journalism and in social sciences academia, particularly at the former polytechnics. Genuinely strange and extreme arguments tending towards a frankly mystical attitude towards biological essentialism were common right from the start, as was a tendency towards disturbing behaviour, the best known example of which was the decades-long campaign of harassment against Ted Hughes.
However, I read one of Rowling's longer public utterances on this for myself and she actually mentions radical feminism in so many words as an influence on her thought, so BRTD's "but technically"-ing the definition of "TERF" is simply inaccurate in her case.
Oh she's clearly fallen deep down that particular rabbit hole. She is unusually obsessive even for a writer.