This isn't a glitch... Your just in low detail, and in a crowded area.
And I saw like 30 people doing this together in world 2, and I do it all the time.
And I love doing this, Idk why, like you said it just looks like your floating above everyone.
No, it's because he's in the Grand Exchange. I do skill cape emotes there all the time, and it doesn't show any objects. Like the Cooking emote, it doesn't show the pan that you're flipping something with, just your hands doing the motions.
In a crowded area on low detail a lot of emotes loose some of their visual effects. For example when I do the 99 woodcut emote at the ge I'll be doing the chopping motions, but without a tree in front of me. Its not a glitch.