If you put Magus in your party, you'll probably notice that nobody in 600 AD does so much as even look at him funny, save for mystics perhaps (and I will continue to call them mystics!). Walk right on into the castle with him sometime.
I'd imagine other people might have come to this conclusion too, but I think the reason for his lack of attention could possibly be that nobody knew it was him to begin with. The only likeness of him you see in that era is a statue tucked way deep into the cathedral, which most people either will never find (secret door) or will be too scared of venturing that far. Magus probably struck by night, if ever. And people generally would not see Magus and live to tell about it. (or at least talk much of it if they really aren't comfortable... ...gleeeeennn...) So, if Magus walks casually into the castle, as long as Crono or Lucca or someone is with him, nobody thinks anything of it. "Oh, another friend of Crono's." Let's go hit up the inn!
