Repeated ping bug

I’m trying to get to the bottom of why this page sends repeated pings. The ever lovely gRegor has been kind enough to let me know about the problem.

So far, I’m scratching my head, but I have a few leads. If my wild guess about the underlying reason is right, gRegor should get just one mention. Fingers crossed.

If isBrill is behaving badly by sending a naughty amount of WebMentions to anyone else, please let me know.