Here is a Homily about Laughter by Archbishop John Shakhovskoy of blessed memory.
There are two kinds of laughter, light and dark. They can be easily distinguished from one another by the laughing person's eyes and smile. You can also distinguish the two within yourself by what kind of spirit accompanies the laughter. In the absence of a light joy, a subtle feeling of light-heartedness, the laughter is not light. If what you feel within your breast is coarse and dry, and you are wearing a crooked smile, then the laughter is filthy. [That type of laugh] always follows some type of joke, something that mocks the harmony of the world. Distorting harmony in the world also distorts one's soul, and that is reflected in one's twisted facial expression.
Woe unto you that laugh now! For ye shall mourn and weep. (Luke 6: 25). Ye shall weep! For you took joy in what you should not, in what merits torment.
"A serene smile," is the mirror of discovered harmony. The saints smile without laughing. Laughter, as the fullness of clean joy, is the condition of the age to come. Blessed are ye that weep now, for ye shall laugh. Ascetic experience in one's enlightening and transfiguration even recommends smiling without showing one's teeth (better to have a little less joy than to have even a fleeting moment of impurity therein!)
"Joking laughter" - the laughter heard in films, theaters, at parties and soirees, casually ridiculing one's neighbor, laughing at weaknesses and human dignity for the sake of amusement and to forget sorrow, pointless laughter, and vain ridicule of others - all these are a spiritual disease. More precisely, they can be characterized as symptoms of spiritual disease.
In the world of the spirits are unclean spirits, spirits seen in the faces of those roaring with laughter… Angelic joy puts a smile on the face. Healthy laughter can quietly dissipate the gathering clouds of evil argumentativeness, enmity, and even murder... Good laughter restores friendships and the family hearth. Caustic, sarcastic laughter is not of God. A sarcastic smile, biting sarcasm, is a mockery of the Gospel salt of wisdom. It is mockery contained in a twisted smile.
Words of sharp witticism always cut open the soul. Sharpness is sharpness whether the knife is held by a surgeon or by a brigand; yet it can be used to diametrically opposite effect. Incision can allow in the Heavenly Light and the warmth of the Spirit, can be employed in order to excise rotting tissue and to ablate necrosis. Yet there is a sharpness that is not beneficial, one that cuts, carelessly cuts up the soul, and often kills.
Only the saints are incisive, and only the holy is incisive. Unclean spirits are a mockery of incisiveness, and many people in the world hone their ability to speak their minds with such wittiness, such [mock] incisiveness.
The boundary between clean and unclean laughter is "Homeric laughter," cackling, roaring laughter... This is the kind of laughter encountered at opulent banquets.Who is vigilant, remaining pious in cognizance of the Mystery of his life, will be vigilant with respect to his entire life, including his laughter. Before God, he will even watch how he smiles. For him, and with the help of his invisible protectors, everything will be clean and bright.
Just like children, the saints illumined the world both with their weeping and with their smiles. Only children and those who have true love for Christ possess that purity of life that can be seen with human eyes - seen even in their facial expression. For children as yet untainted by the spirit of corruption, everything is direct and pure. For them, death has not yet revealed itself to mock their mortality. They still possess the spring of life both as a beginning and a memory of Heaven. Thus, their vision and laughter is clean and pure, they speak without dissembling, they find it easy to weep, and to forget that they had been weeping... "Except ye be converted and become as little children, ye shall not enter into the Kingdom of Heaven…" The reason is clear. The greatest praise for a person is "He has the laughter of a child"… incorrupt laughter, approaching Heavenly harmony.http://www.stjohndc.org/Russian/homilies/HomiliesE/e_Laughter.htm