Last modified: 2013-09-09 19:56:54 UTC
As one can see on the URL provided, when browsing the thread history page, on the "Comment text edited" diff link it points to HTTP instead of HTTPS. Looks like a hardcoded protocol.
Gerrit change #50714
Patch in Gerrit needs review...
Change 50714 merged by jenkins-bot: Comment text diff links in thread history should be protocol-relative https://gerrit.wikimedia.org/r/50714