I went over and took a look at some of the postings, in particular the one you singled out and took an excerpt from.
I will state a few things, as they've been explained by people I trust in these matters.
- What are most commonly called the "passions" are the natural energies of the soul, but operating in a fallen, contra-natural way. Thus, if one wanted to be very specific, you could speak of "fallen passions" and "non-blameworthy passions." However, most spiritual authors (in particular the Fathers) will speak of the fallen ones simply as "passions", and only rarely speak of of the non-fallen manifestations of these spiritual energies/activities as being "passions" in any sense.
- There are certain energies and capacities of the soul, not to mention of our lives, which while not always blameworthy, are strictly a part of this fallen world, and will pass away. One example is our capacity for fantasy, or the "phantasms" we form in our mind after perceiving things. While strictly speaking this doesn't have to be a bad thing, it is a way of knowing which will come to an end, and it certainly is prone to causing problems. It is where logismoi take up residence. While this term is often translated as "thoughts", it really refers to thoughts/images formed in the mind which have a certain effect on the passions. Because we are fallen, we have a tendency to distort these unwittingly, or be vicitimized by them (when they are associated with past sins, or evil things we've beheld in passing.)
- Christ our Lord experienced the unblameworthy passions. Now strictly speaking, this did not have to happen. For example, when the Saints go into the condition of theoria (vision of God), even in the Old Testament times (as Moses did atop of Mt.Sinai, where he stayed atop the mountain with no food or water for fourty days, communing with our Lord), natural/worldly processes will be suspended. In fact in such a state, they get a taste of what the renewed, ressurected life of the saints will be. They are not harmed by the elements, they are not harmed by lack of food or water, etc. Also, they know perfect peace. It is because of such a profound experience of grace that the God-seer Moses could stay atop of a fiery mountain as he did with no food or water, or why St.Simeon Stylites could stay atop of his pillar as he did, or why St.Seraphim of Sarov could enter into the incredible ascetic acts he did.
- Part of our Lord's kenosis (condescension) was not simply Incarnating (taking on a human nature - body and soul), but also allowing Himself in His Humanity to experience the "passions" (as in the unblameworthy ones), and doing so without ever sinning (an incredible thing!). This is precisely why, for example, He could taste the bitterness of suffering and exhaustion beginning in the Garden of Gethsemene, and as He carried the Cross, or upon being crucified and dying. Where as after the Ressurection, I guess you could say His humanity enjoys a condition like that of the Saints who enter theoria, but even "more so"...thus why He had a body which while still a physical body, was a "spiritualized" one (appearing wherever He would, passing through walls, doors, etc.)
I'm explaining all of this as background - one has to know what we fell from, where we are, and what our future is, to "get" what the Fathers generally say about laughter.
Laughter is a passion obviously, and while I don't think it's always blameworthy, it very often can be. We tend to find humour in the misfortune or foolishness of others. At best, while humour obviously isn't always bad, it is something that will pass away. Thus why at least in the Jordanville prayer-book's daily examination of conscience/penitential prayer, "immoderate laughter" is mentioned as a sin. Is it the worst thing in the world? Perhaps not, but neither is stealing a pen - but it's still a sin.
One thing that's hard to shake from even very "conservative" western Christian (heterodox) backgrounds, is a legalistic attitude about sin. Such a view has two tendencies, often at work at the same time; on one hand making people very intolerant and "rule crazy". On the other hand though, it creates a kind of self satisifcation and minimalism - feelings of "well, that's not really a bad sin, so who cares?" I'm not saying that this is officially what these heterodox religions want from their followers, but they do engender this attitude. This mindset also creates all sorts of hair splitting, where the spirit of intent of things gets forgotten, and people can become smug or content in their current state and stop actually struggling onward. It's kind of funny that two such different manifestations can come from the same attitude, but it's been my observation and that of others much wiser than myself (which isn't really that difficult now that I think about it.)
Christ our Lord, while experiencing un-blame-worthy passions, and really and truly struggled and mastered them (as a perfect ascetic), also did not indulge necessarily everything which this current age grants us. Thus, He did not take a wife, and enjoy marital relations (which are not sinful obviously, but neither are they a part of the future life). It's the same reason why monastics do not marry - not to say marriage is evil, or that what goes on within a good marriage is bad (indeed, to say such is heretical) - but because they're trying to live the future life, the life to come, while shedding their sinful ways and acquiring the spirit of silence.
I don't know that Christ never laughed, but I don't find evidence of this in the Scriptures either. Nor could I picture Him being overcome with any immoderate, blameworthy passion, precisely because He was without sin. It's also worth noting that the "laughing Jesus" image was a hallmark of heretical gnosticism - this having to do with how they misunderstood sin, our relationship to the body, etc.