I personally have never kept one, but know others who have. They are generally reef safe (as much as can be) because they only eat free floating material from the water column so it is against their nature to eat coral or anything else like that. However, if underfed they could do anything, but I'd give a guarantee that they won't touch corals. At least, I'd bet money on that and most fish I wouldn't do that on.
I did take care of a female swallowtail for a time (same genus) while someone was making changes to their tank and it never even looked at corals. Also didn't like nori, but was a model citizen.