brembs

@paulcalcus: Yes, I looked through all relevant .htaccess files and found an offensive entry. It seemed as if it had been there all the time, but apparently without any effect until I de-activated and re-activated Jetpack. Curiously, the entry was added by a security plugin, where I explicitly clicked on a button to allow for XMLRPC. After I commented the entry out, Jetpack stopped complaining and the security plug-in showed no change in behavior.
<shrug>

If the theme author is no longer around, how can I find out which component is causing the warning – is there a debugging button somewhere? I’ve used something like this on other CMSs…

Jetpack has been working fine for years now. Today, I just deactivated all plugins to troubleshoot an unrelated problem and when I reactivated them Jetpack started to throw this error. Of course, no settings have been altered in the few minutes between deactivation and reactivation. Where could that problem now possibly lie?

“What exactly do you mean?”

I mean if I take the original code from the original author and replace it with your code, I still get the same error message, as if I hadn’t changed anything.

Inserting this code at that place had no effect on the error message whatsoever, I’m sorry. But thanks for trying to help us all out!