Date & Time: July 3
Frequency: Constant
World name: Leviathan
Character name: R'din Tia
Class/Level: SCH/100
Party or solo: Solo
In-game time: 10:27
Area and coordinates: Any area
Steps:
1. Be a Miqo'te (possible female only, other races with tails may also be affected)
I have not tested anything beyond female Miqo'te
2. Wear Lix Chiton (chest piece added with Occult Crescent)

From what I see the Lix chest piece removes tails from character models, but the similar designed and in appearance Tycoon chest piece from the same vendor, added in the same patch in Occult Crescent does not remove tails. So many chest pieces with capes just let the tails clip I can only assume this is a bug.