A new Season 3 item, Statikk Shiv, deals magic damage that can critically strike. Does this critical strike get counted in with regular critical strikes on the end-game stats screen? Or is it just considered magic damage?
Critical strikes are not tracked separately, only your largest critical strike.
The summary screen breaks damage up into Physcial / Magic / True (though only the first two are tracked explicitly), but this has nothing to do with critical strikes.
So it crits for more damage... which is irrelevant as far as critical strikes are concerned. (And you'll be hard pressed to find a case where the 100 magic damage crits for more than your basic attack in the first place)