In case it helps anyone else coming to this thread: I found it was that it only tries to use turnstile when there's a link in my comment. I had a look at the code and could see that it would only try to use turnstile when the server says it "needs turnstile" (and that's where it breaks, because the developers forgot to wire up their site key). Guessing what the condition was when the people here can clearly comment _some of the time_, I took the link out of my comment and it worked.