Hitboxes are always the same. Doesn't matter if the player is taunting or not.

Nova is right and plus every taunt would be like that, and if you really think, it would be better that way because it would be like you hitting his hovering machine so then he falls off and then ded

To be fair, if this got added people will probably find ways to exploit it by exiting the map.

When was there a time where you can exploit with a taunt that isn't doesn't have a weapon with it? (ex. Eureka Effect.)

This is not how taunts work, Taunts are like hats. They change absolutely nothing. When a taunt is used, the players model is moved to adjust to the taunt, (see balliniboucner) But the hitbox still remains in the exact spot where it is. If you were to heal someone using a taunt that moved the model further than the exact default spot is, you can see the medigun heal end point orb clearly visible as it touches the middle of the hitbox, not the model.

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Yeah, hotboxes are broken on a lot of not moving taunts, and that also why they broken in record mod. Carts, tank and scout's pogo are exceptions, they both moving and broken.

Even if they were to fix hitboxes to be with the model on taunts how would that break the game? For this one for example all you need is for there to be a collision box for the hovercraft which would stop the entity from going over or under areas considered unaccessable. Or other ways that stop the hitbox from glitching like having it teleport to a valid space (so they won't teleport into walls) and have the model end. Sure, sometimes this may disorientate the player but majority of times the hitbox would teleport where the player should land.