Quote Originally Posted by Enkidoh View Post
His Exarch outfit lacked a tail and as he wore his hood up for much of ShB, it completely disguised the fact he was a miqo'te (or mystel) so people just assumed he was a partially crystallized hyur (or hume) - Crystarium gossip though mentioned that people could swear they saw the hint of a tail peeking out under his robes, and that he apparently hid it by wrapping it around his waist like a belt.
It's Moren (in the quest In His Garden) that tells you at one point that he sometimes caught a glimpse of what must be a tail.

There's no reason at all to derive "wrapped it around his waist like a belt" from that, though – on the contrary, it suggests he simply had it concealed under his robes and sometimes failed to keep it where the fabric wouldn't drape over it.

It might be possible to keep a tail out of the way by curling it around a leg, but not around his waist – which in any case would create more of a conspicuous lump than simply hiding it in the loose space under the skirt of the robe.

Robe being the key part here, as it's a very different matter to supposedly hiding it under a skintight outfit like the Phoenix suit.