comment form: "this content will be transmiitted over an insecure connection" warning

Setting "Switch back to http pages when there are no matches" and in combination with a custom url rewrite that adds an extra path element to certain node pages. The comment form is altered to have an absolute destination that is http, even when the node the comment is being submitted to is https. This gives an ugly: "this content will be transmiitted over an insecure connection" warning

This error will also happen if, for example, I manually put an https path in for (e.g.) a forum node and then submit a comment.

I think a more correct behavior is to let the form action be https if the current page is https.