I have to second what @dibbles said...you didn't say that. You have to remember that there are thousands of people around the world who use this site as a reference resource. They may search for "can I use aluminum foil to insulate my soap" and your post above will pop up and they will think "it's okay" and move on. It's part of the reason why my posts can get a little 'wordy' at times, because I often include the 'why' of what I do or don't do. Like I use cookies sheets and baking trays to cure my soaps, but I always mention that they are double lined with freezer paper because I don't want folks thinking that it's okay to use them without.The foil doesn’t touch the soap, I put cling wrap on first. The foil is to insulate it.
And even with plastic wrap/cling wrap/saran wrap...I still would NOT use aluminum foil on of the off chance I got any raw soap batter on it because even a small amount is going to cause a reaction. Maybe not enough to cause a danger, but why take the chance when there are so many safer alternatives available?