Why am I now seeing these mysterious alpha-numerics in the 'YouTube' comments section?

XAI780K

Like here, for example.

[media=https://www.youtube.com/watch?v=STBSaDn_q8g]

An example.

@NandanOber
2 days ago
Peirs was absolutely obliterated by Mearsheimer. Like stepping on a snail crossing the sidewalk. Who of you also got into XAI780K today

What the hell is that?