It's not an emote, but a glitch - 't-posing' is the default appearence state of character models in the game files without any animation loaded, but it's not meant to be seen by players as animations are meant to be 'on' at all times, so if you see it happening to your character or others briefly, it's usually simply due to bad server lag and/or a slow PC that is taking longer to load everything including character animation files (1.0 used to do it bad, due to that game's badly optimized engine and laggy server code). It's simply a glitch.