QUOTE (Brainpiercing7.62mm @ Dec 16 2010, 04:29 PM)

That's already out of the way: In 4th you're noticing the mage using the magical skill. In 20A you're noticing "sparkles" (and all the other stuff). Clearly the former doesn't work if the mage is hidden or invisible, while the latter is obvious even on invisible mages.
The text is identical in both books, except for the one new line in the Anniversary edition explaining why more powerful magic is easier to spot.
and nothing in the text say that noticing doesn't work if the caster is invisible.