It is fine for them to touch. This is something you can regulate rotating the position of levers around the handlebars and also the angle of the handlebars. Having the levers stick out more to the outside makes them easier to operate but can impair the fold. You need to go for a compromise. If you are worried that the fold is not flat enough, loosen the bolts that hold the lever position and tighten them when the bike is folded and you are happy with the flatness of the fold.