Tooltip error on "Binds to Account" items

Some items, such as Nebula and Aurora drops from Carnival, are "Binds to Account", ie tradable to anyone until consumed*. The tooltip shows "Binds to Account" to the person holding the item.
However, when linked in chat, the tooltip shows "Bound to Account" to other people.

This spawns the following conversation approximately 60 times an hour in chat during Carnival:

Alice: WTS [Nebula]
Bob: That's bound
Chuck: That's bound to account, you can't sell it
Mallory: You can't sell that
Eve: Guys it's not actually bound
Chuck: It says bound to me!!
Eve: Check your Auction Hall, they ARE tradable, because the tooltip is WRONG to us
Alice: WTS [Nebula] (YES IT IS TRADABLE!!!)


* I do not understand what "Binds to Account" means in the context of a mount, since it's not tradable at all after collection, so why not remove "Binds to Account" from them entirely?

This is really confusing. All offered mounts in the AH are "Bound to Account". After I bought one, it was again "Binds to Account" and tradeable. I tested it also today, after Sharandra´s Question.