Chameleoman, you have your answer. Don't put substrate or your cham will eventually eat it and that will cause an impaction. substrate also breeds life-threatening bacteria-chameleons live in trees and do not regularly interact with ground substrate. end of story. i thought my cham would never go to the bottom of the cage. for 10 months he didn't...then one day, BAM there he was, in the pothos on the floor. he ran up immediately when he saw me, but that proved it to me: just because you don't think it will happen does not mean that it won't. you are not all-knowing, none of us are. do you know for a fact your cham won't eat the reptibark? it definitely looks like bugs from a distance. sooner or later, your cham will eat a piece. maybe intentionally, maybe accidentally. how it happens is irrelevant, just that it does. then you're in trouble and will have to take your cham to the vet. common sense at this point.
this forum is a fountain of knowledge. people here give you trustworthy advice for free. you don't have to listen to advice given here, but if that's what you're going to do, why post in the first place? when i get advice here, i take it into consideration.
i'm baffled when people whine when they get life-saving advice. it makes them look infantile. then they complain when someone calls them out on it. just suck it up and keep the floor bare.