Additional information: this bug appears to occur on any mount that uses the same sitting animation as the Company Chocobo, as it occurs under the same circumstances with the Draught Chocobo and affects both players if there is a passenger, but does not happen with the Ceremony Chocobo, which uses a different animation for the rider in front (at least for female characters in our testing). The change is visible to any player who is in the zone when the walk left and dismount sequence occurs, but not to players who enter the zone afterwards. The size increase appears to be between 25-50%.