As someone that t-bags I can say it's literally none of what OP is saying. It's online video game tradition. It's a challenge and a warning at the same time. It's "git gud" before "git gud" was a thing. No one means harm by it. They want you to notice them. Find them, challenge them again. You delved into the realm of competition. You must play by their rules. Fight them with every ounce of your being. And when they are sprawled out on the ground, walk over to them, find their face, and make sure they smell your victory.
Anyways, in all seriousness. I don't t bag outside of frontline and rival wings. Feast is easier to spot and pick out names. Last thing I need is some poor sport to report me. Tbagging is the least offensive thing folks do. Just be thankful you can't hear or read what folks have to say.