I'll start by saying that I don't have any experience at all growing this plant - warm, swampy, and muggy is just about the furthest you can get from good ol' Irish cold, wet and windy. So I watched the film Adaptation with fascination and then turned to orchids I actually had a chance at growing with my conditions and resources.
Having said that though, I've been reading this thread with keen interest, and I have a few comments:
1) Ray, I didn't interpret gdupont literally implying that orchid growers lose their minds over rare/difficult species. By putting "lose their senses" in quotes I think it was clear they were just using a turn of phrase that was ofc, exaggerated. I think what they were trying to get at is the general tendency for us human beings to be weirdly competitive and sometimes overly enthusiastic when it comes to things that are perceived as a challenge or valuable. Even in something as calm and slow-paced as plant growing, we find ways to compete with each other: "I bloomed this super rare plant; I have this massive collection; my plant is a specimen plant..." etc. And then we even want to judge plants and hand out awards. The victorians went around laying waste to forest and jungle just so other collectors could not also bring home the same orchids - orchidelirium was indeed a thing. I think it's therefore fair to say that people can get a bit carried away sometimes.
2) I completely agree that data shouldn't be disregarded. Just because the temps seem too high is not a scientifically sound reason. Data is data.
3) No one has mentioned dew point. Perhaps I'm being silly here and everyone is implying it by talking about humidity - Ray mentioned condensed humidity. When the air is sufficiently saturated with vapour we reach dew point, and the point precipitation can occur. We can easily observe water being condensed back out of the air when having a cool glass of something refreshing on a hot day, and the higher the humidity, the more condensation we see. We also observe dew point often between the change of temps at sunrise and sunset when we see dew form on grass or other vegetation. We know that the higher the air temp, the more carrying capacity it has for water vapour, so in somewhere like the Everglades, we know the air can carry a lot of water vapour.
I was born and raised in Johannesburg, South Africa, and although the air temp is warm nearly year round, Joburg has quite low relative humidity - why is that? Because of the city's height above sea level and the high-pressure weather systems that area tends to have. It makes the heat very comfortable and easy to manage as a human because our body's ability to cool itself by sweating and evaporation gets to work as intended. I go on holiday to Durban, however, and it's quite a different story. Although these two cities have a similar air temperature, there are some important differences: the city's at sea level, and the ocean it borders is warm (Indian Ocean). The result is relative humidity that rarely drops below 60%, and is consistently in the 80s in summer. This creates a very high dew point, and makes it very uncomfortable for anything that needs to transpire to regulate it's temperature. It also means water will condense out of the air extremely easily. Anyone who has hung out their freshly washed laundry to dry outside in Durban will know to bring that laundry back in before the sun starts to dip, because at the slight dip in temp at sundown all that vapour in the air will happily condense and be wicked back into your dry clothes. And although your clothes won't be as wet as when you first hung them out, they will be sufficiently wet that you will have to put them out to dry again the next day. So my point here is, even without heavy rainfall, dew point is going to be high in the Everglades, and therefore water will readily condense out of the air onto surfaces that are cooler and drier than the surrounding air.
4) That brings me to my next point which I've already touched on and which Ray already mentioned - high humidity reduces transpirational loss. Air at carrying capacity cannot readily take up more vapour. I'm massively oversimplifying this, but broadly, plants rely on the system of transpiration (in conjunction with other things, like the cohesive nature of water) to create a pull from their roots, stems, and leaves to create osmotic pressure, and allow water to move through the plant (it's vascular system). We've all seen when this system gets broken where a plant with a long stem will wilt over in the heat, and we immediately realise that the soil the plant is in is too dry. The rigidity that the plant maintained by the movement of water through it's system disappeared because there was no water to absorb through the soil. We've also all learned to recognise the signs of a stressed plant when, say, an orchid that doesn't have a good root system casts off some of it's leaves. It's the plant's way of trying to balance itself and allow it's vascular system to work more efficiently - if the leaves are using more energy and losing more water than the plant can sustain with it's limited roots, it becomes detrimental to try and maintain all of those leaves.
Now, what about a plant that doesn't have any leaves? It's vascular system must get kind of interesting - it no longer has leaves to carry out photosynthesis and facilitate the evaporation of water through respiration, so it certainly needs less water to maintain it's structure and the leaves themselves, but then it needs another means to feed itself. In the case of Dendrophylax lindenii, it's root system is primarily responsible for it's ability to transpire and photosynthesise, and the roots have some interesting differences to do this. When I look at a plant like this, I'm reminded of how nature is "lazy" - I don't mean literally lazy - I mean that a system will always maximise energy i.e. use the least amount of energy possible to do a necessary thing so that it is as efficient as possible. With reduced need (and ability) for transpiration to occur due to the high relative humidity and high dew point, this plant has reduced it's reliance on traditional plant structures, such as leaves. It also means that roots cannot stay damp for too long, or this will impact the transpiration the plant can perform, and the roots will likely rot. The fact that these plants are endangered in their natural habitat means that this incredible specialisation can be massively impacted by any disturbance of those conditions, causing damage to the population - ofc, figuring out their growing conditions is what has created an interest and challenge for many orchid enthusiasts.
5) So, this brings me to the subject that's been mentioned a number of times - mounting materials and methods. I suspect, based on observing pictures of this plant in situ, that this plant supports it's vascular system, at least in part, by the way it appears to mount itself to it's chosen medium. The radial pattern of it's roots maximises surface area, and therefore maximises it's ability to 1) transpire in such a humid environment, 2) make use of available light for photosynthesis, 3) make use of whatever precipitation is more readily available, whether rain or dew, and 4) ensure even drying so roots do not remain sodden. There is a possible no. 5 that I'm a bit uncertain of, but I wonder how the way the orchid attaches itself so closely to something relatively large like a tree trunk may also help, such as perhaps helping to regulate the overall temperature of the plant by making a small plant less susceptible to fluctuations in ambient temp and preventing it from succumbing to "temps that appear too high for an orchid". I therefore believe that the mounting material and the way it is mounted is absolutely key.
Ray already mentioned a grower having more success with hard cloth than a cork mount, and jtrmd mentioned using a piece of white oak. White oak, from what I understand, is incredibly resistant to the absorption of water, and therefore unlikely to be saturated. In the absence of leaves, and in the presence of incredibly saturated air, evaporation and respiration must occur somehow. It makes sense to me, then, that along with whatever air movement is available in the immediate surroundings (because there is still air movement), a surface that does not readily absorb water, or at least becomes saturated at a much slower rate, may create a small amount of additional air movement via a drying effect - water will dissipate from a non-absorbant or partially absorbant surface faster than an absorbant one. I have some ideas about how this may help in a closed system such as where people are using closed jars or fish tanks where there is no air movement occurring from external environmental factors, but it would all be conjecture. But really, this is all conjecture unless I try it myself, and even then, the ability to definitively state what works/doesn't work would be anecdotal.
Anyway, for anyone who's made it to the end of this post - thanks for indulging my musings about this. I'm tempted to try this plant myself now, but it seems incredibly difficult to get a hold of in the EU.
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