Yes, my desktop was able to "sense" the "plug-in". That proved the little contact in the connector was working. It has nothing to do with microphone working or not.
No, I am not going to try your suggestions. I just don't see any logic behind your steps.
I have 3 different desktops from 3 different vendors, Intel (i5, 1155), Gigabyte (i3, 1156) and Zotac (Q9400, 775). They all have Realtek audio and they all have the same issue. Oh well, I still have my Lenovo Thinkpad X61 for Skype.
Nowadays, people dealing with digital hardware or software don't really have much idea of analog any more.
I will consider RMA this motherboard. However, I doubt that will do any good.