My reference pronunciation has always been like the word "watt", deadpan, with a blank face while staring into space.

I tend to agree with this, but in the circles I run in where it was used it's also spelled 'wut'. I was a little confused when I first saw it here on HN as 'wat'.

Properly? References? Anyway, who cares, it's funnier to say when you sound it like "cat".

"This just perpetuates the mispronunciation of 'WAT'."

What a silly thing to pretend to have any knowledge over. As if there is a consensus, or any authority by your part on the matter.

Homographs.