Folders can indeed be used for touring. I've used my Bike Friday Tikit for light touring (i.e., no camping). The Bike Friday New World Tourist is built for full touring, although it's not a quick fold. All BFs are on the expensive side, so look elsewhere if you don't have a respectable budget.

In terms of a comfortable bike that can haul a lit of stuff, you'll get an equivalent non-folding bike for a bit less. The advantages to folding touring are many, though - shipping your bike to the starting point is greatly simplified. No more minivan rentals!