i could only just hear a voice quite near say
Id always speaks slowly, deliberately. That's no secret, and Bart's sure he means to impress upon people just how serious and singular (if you'll pardon the inconvenient double entendre) xe is; not to be trifled with, nor confused for either his fellow alter or that bygone Demon, when it isn't wholly appropriate.
Xe can never intimidate Bart as much as he'd likely prefer, though. Bart might jump a bit at a soft, darting intonation behind his shoulder (never behind his bad eye, though - Id plays fair!), but he practically refuses to cower.
Id won't be goaded, either. Perhaps...understood, however.