You mentioned that you tweaked things a few weeks back and fixed the issue, but I noticed today that your site is hitting http://mention-tech.appspot.com/ pretty regularly and still automatically sending what appear to be hundreds of old webmentions. I’m not sure what you were using to send them on your behalf or what your tweak was, but thought I’d mention it if you had previously used Kevin’s service and either forgot to turn it off/disconnect it or something else odd was going on.