Jetpack “Connect to WordPress” serving insecure content under HTTPS

Well, this was about half my fault half Jetpacks’. WordPress in general defaults to non protocol-relative URLs (eg http:// not //) and the problem was an explicit http:// image I used Jetpack to insert into my sidebar. Moving that to a protocol-relative // cleared up the mixed content problem.

In general keep an eye out for those kinds of non-relative URLs, I had to redo almost every image URL I had used on the site to get rid of mixed content since WordPress defaults to leaving those in there.