The Brief: K stands for "okay."

DEEP DIVE
K stands for “okay.” In texting, it is generally considered a curt or passive aggressive response due to its failure to convey enthusiasm. K can also be used to communicate irritation, annoyance, or ironic indifference; such uses include “k thanks” or “k bye.” If K were an emoticon, it would be the bored face π
Found myself wondering what was considered the catchiest song ever
So I looked it up
Supposedly it's "Wannabe" by the Spice Girls
That answer popped up a lot. Studies showed people recognized it in 2.3 seconds (average is 5 secs)
Anyway, that's what I discovered… kbye
— Joseph Gordon-Levitt (@hitRECordJoe) January 28, 2019