tl;dr: Having both AntiSpam Bee and Jetpack Comments causes this, disable one or other
While trying to leave a comment on here on a previous post, I got an error:
Invalid security token
Apparently, AntiSpam Bee and Jetpack Comments are not compatible. I’m not sure when Jetpack comments were enabled as I’ve had relatively recent comments/ I will see if I can find an antispam plugin that is compatible with Jetpack comments, or disable those.
My sincere apologies to anyone who has tried to comment and not been able to as a result!