Just to clarify. This is a thread about HDMI, but your answer is specific to display port yes?
If so exactly which kext are you talking about please?
I am using the one referenced in the very first post in this thread, then relinked later because the original download link was broken. HDMI Audio 1.1 is what enables Audio over DP also. Very technically, the same kext enables the same card and the same monitor to have audio over HDMI where it would before. I just have to use the other cable and the other input.
This is covered in the thread. While I would normally let you slide on a TL;DR over a 25 page thread, you DID have to read through a few posts to find the new link. That should have been covered.