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If you aren't convinced, then I insist you build a compass like I did, take your camera outside, have 4 friends hold up signs indicating the four directions, take a panoramic photo, and show it inside your sphere. Show it with U_Scale = 1, and with U_Scale = -1. I guarantee you, that U_Scale = 1 will be backward on your sphere, and on the Poser sphere.

I match my light for years using this and it always worked perfect and with right direction, I do not use panoramic pictures that are merge God know wish direction .. I work on my own Light probes in area where I know the durections and what I see and where the light coming from... look the Ballisma image in my garden, the light was where it is in real when you look on that, everything was correct from the reflections in the sphere to the light.. how I can more say about...
you can't base you words on a panoramic images b/c you don't know where the photographer started merge it so don't accept it will fit the standart with the mapped sphere I did...that was bassed on the directions of the world map and globe.. ( the same as the Light Probe)
if you gonna flip the world then please do nobody will kill you for that...  hahaha if i do the same
my light will be not matching in my images no more..so... I not agree, I am sorry

P.S I give you honor back regardig the info about UV_scale IBL, you did mention that we all missed that...

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"Surrender to what it is - Let go of what was - Have faith in what will be "