My opinion is that unless a quality is permanent, it's not something worth mentioning as a stat. A footnote in your background, yes. This most definitely includes "Aspected Magicians" who aren't aspected but simply haven't unlocked their full potential; that's what attribute, skill and gear selections are for. That kind of "Aspected Conjurer" is just a magician who hasn't discovered his full potential or invested very much of himself into Sorcery or the other magical arts. They're not a magician who is metaphysically handicapped for life... which is what the negative quality represents. Just like the Mystic Adept who only spends points on Adept Powers in the beginning because he doesn't realize he can cast spells or conjure spirits yet. Or a Hacker who's only focused on being a Drone Rigger. Or a Street Samurai who hasn't discovered he's a crackshot with a sniper rifle. Or any other concept that can be "fixed" simply by buying a few skills or pieces of gear.
Of course, I also forbid qualities (both positive and negative) that don't fit in with that, too. Incompetence is just a fucking joke and right out (as are Infirm and all the other "free points for just not buying any skills or raising your attributes very high" flaws). A Day Job is a background note and covered by your Contacts and Knowledge (or sometimes Active) Skills. Enemies are just inverted Contacts so are allowed, but are treated exactly like Contacts as to what happens when you lose them. etc.