Unlike a normal mount, the illusion mounts are not able to determine if you are flying, and thus cannot swap out of the illusion when on the ground, and back when you start flying. Thus to prevent players from walking in midair, the cannot be hidden. We are working on a change that should be in for the next hotfix that will allow an appearance mount to continue to respect the hide mount option, so any player that want to hide their mounts will be able to put a non-illusion mount into their appearance slot and do so.
Thank you, Caith! Dare I ask...will that fix the underwater issues as well? (I'm guessing probably not, but figured it wouldn't hurt to ask)
