Here's something I noticed while testing a client-side fix for this issue.
If you follow a permalink / shortcut URL with an
https: protocol, like:
you'll get redirected to:
even though, in fact, the
https: version of the target URL would work just fine. This rather frustrates any attempts to fix such links in post text to use HTTPS.
The same happens with other similar shortcuts too. For example:
However, other non-permalink redirects do retain the correct protocol. For example:
correctly redirects to:
It seems this is because those redirects are actually using relative URLs in the
Location: header, which, while not strictly speaking allowed by the HTTP/1.1 spec, does seem to work in most modern browsers. Presumably, the permalink redirects could be changed to work the same way.