To my faithful student, Twilight Sparkle,
While Laughter is a virtue and can greatly ease pain and fear, there is a time and place where it is justified. The death of a pony, especially one who has yet to enjoy the wonders of life, is a terrible and painful event, but a certain level of respect is warranted for the pain of the family, and the possibility of what might have been. It may be appropriate to point out how much fun the little colt or filly might be having in the Summer Lands, or offer words of comfort intended to make a pony smile. They should not be disparaging, unrelated, or insensitive.
An older pony, on the other hoof, may have desired others to laugh after they are gone, and tasteful jokes, or reciting one of the deceased pony's favorite jokes is a good way to honor that pony and make others around you feel a little less pain.
I know you can do better than this Twilight.
Your loving mentor,
Princess Celestia.