Spirits [i]can[/i] be visible to everyone under certain conditions: for the spirits to be visible they have to leave the Guardian's body in chunks, that is, several spirits tied together in a single mass. This will appear as a small, transient piece of sheet hovering or 'dancing' in the air around the Guardian, emitting a faint light of some color or several colors. However, this will not happen unless the spirits feel safe with the environment, which is another 'proof' that spirits are sentient. In most cases, the spirits will only be visible to others when the Guardian is alone somewhere, or when there are 'trusted' people around (such as our characters), but strangers will shy the spirits away. So, if Remi walked into a room with only our characters in it, his spirits [i]could[/i] emerge, but it is not a certainty. But if and when they do emerge, spirits are very warm and loving to their Guardian and 'trusted' people. If they touch you while 'dancing' in the air, in their 'physical form' outside the Guardian's body, it will feel like a warm piece of silk caressing the skin.

Edit: I think there is some Chinese (?) tradition of dancing with pieces of silk tied to sticks? I've seen it somewhere. Those pieces of cloth is what I imagine spirits look like. I'll see if I can find some video of it.

Edit 2: I found a video [url=http://www.youtube.com/watch?v=vYz9PuO1eCk]here[/url]. They start to dance with the silk strips at 1:22.