That doesn't make sense, think HN/Reddit/etc, which are HTTPS and primarily link to other sites which can (and very often are) HTTP. There is no security compro

That doesn't make sense, think HN/Reddit/etc, which are HTTPS and primarily link to other sites which can (and very often are) HTTP. There is no security compromised here nor any other link between the two than one referring to another. Linking resources (like images, files, etc) is another topic, but it doesn't make much sense to put a barrier for pages. If nothing else, you get annoying warnings that people learn to ignore.