Summary:
An emote can be played while flying with the elytra. This creates sometimes very incongruous player positions (especially with emotes using feet and player movement).

Steps to reproduce:

1. Change the camera to a third person.
2. Put on the elytra.
3. Start flying.
4. Play an emote using the player's legs, all parts of the player, or the player's legs.

Observed results:
When flying with the elytra, the player can play an emote.

Expected results:
When flying with the elytra, the player will not be able to play the emote, and emotes already started (before the flight starts) will be interrupted.
As in the situation when the player gets into the boat.

Image: