> Mozilla and Apple all support it already.

Do you have a source? As far as I know that is not accurate.

This is unrelated to CT; this would still be needed to kill any maliciously issued certificates.

Apple has App Transport Security which allows you to require CT. I think the OP meant Google, as the patch[1] for CT is still pending in Firefox.

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=944175

Right. What I meant was actually that they either support it or are in the process of supporting it. But I haven't heard anything about it from Microsoft.