Date: June 18, 2017 10:20PM
Yes, it's associated with a promise you make in the temple. And it's a general prohibition--not just to be avoided in the temple, but to be avoided anywhere at anytime.
From the temple ceremony:
"PETER: A couple will now come to the altar. (Witness couple comes to altar as before.) Brethren and sisters, this couple at the altar represents all of you as if at the altar, and you will be under the same obligations as they will be. We are required to give unto you the Law of the Gospel as contained in the Holy Scriptures; to give unto you also a charge to avoid all light mindedness, loud laughter, evil speaking of the Lord's anointed, the taking of the name of God in vain, and every other unholy and impure practice, and to cause you to receive these by covenant."http://mit.irr.org/mormon-temple-endowment-ceremony
As far as the precise definition as to what constitutes "loud laughter?" I don't think it's really defined anywhere, like so much of Mormonism. But from my experience, most Mormons don't get overly uptight about it and will enjoy a good laugh now and then.
[Edited for content]
Edited 2 time(s). Last edit at 06/19/2017 12:23AM by lurking in.