Mages [i]do[/i] have some ability to feel magical energy in others, though it is by no means as accurate or strong as the sniffers' ability to sense the same. Necromancers are especially attuned to sensing (and manipulating), magical energy, other mages less so. Even regular people can sometimes pick up when there is an [i]unusual[/i] amount of magical energy permeating the air or someone is harbouring absolutely vast amounts of it (although they likely wouldn't necessarily realize what it is other than a strange sensation, not unlike that which you might feel right before a powerful thunderstorm).
	Gerald as a fairly skilled necromancer has been described to sense magical energy and pick up presences to the point of knowing where people he cannot see are via it (and being rather disturbed when he met the one soulless being he could not sense due to it, well, lacking a soul and hence your typical reserve magical energy) - as long as there is not too much background-noise, such as the magical energy of the trees of the Anaxim forest was, anyway. To a lesser degree, he can also pick up the general type of magical energy someone has in them (not sure about elemental alignment, but he could tell a demonspawn apart), as well as he managed to deduct that Aemoten has excellent self-control due to his soul being in turmoil while he remained externally calm and collected (note that he wasn't awake during the latter). He also "reached out" with his soul at one point to sense things better, and could pick up that the three-quarter demon's human side was in control once more. 
	I'on would not be as good as Gerald at such things - mostly since he isn't a necromancer ... or at least as dedicated and skilled necromancer -, but he'd still fairly easily know when someone has unusually weak or powerful soul and similar. I'd assume he might not be able to immediately pick up that the more mortal demonspawn is a demonspawn by her being near alone unless he specifically focuses on sensing it, whereas the more demonic one would be quite evidently a demonspawn? And yeah... Living beings do "leak" a bit of magical energy, or they'd be "invisible" for someone sensing souls. 
	Jack correct me if I'm off at any point, as always. 

	Ehh... And no need to apologize for rambling. I do so myself often enough. (As long as I don't insist on replying solely in commandline error-messages, all is good. I know how to take breaks and not actually overwork myself.)

	On another note, I actually have a somewhat serviceable post, just waiting for ASTA to greenlight it.