But all those things seem to have meaning only because we want them too. You can do this exercise with every scene in the book and you won't necessarily get anywhere. Maybe there is or isn't, but we're nearly 4 books past it and none the wiser.
Maybe a couple sentences here or there in TAE, but largely the information in this scene appears to be all we'll ever get.
I've read that scene more than any other, i haven't found why it would be gleaming, the light can't pierce the water. Kelhus himself stops trying to pierce the water to see through.
Check out a waterfall some time. If you can, in the dark with a flashlight. Light pierces it but that doesn't mean you can see through it. Same issue with having a campfire in the dark and you can't see outside the immediate circle of light.
Light's still going past where you can see. Its just refracting and too diffuse to make sense of. It can simultaneously make it appear that the thumbnail is gleaming while also being too dim to see through the other side.
Moe sitting behind cataracts of great amounts of water so Kellhus can't see him. Weird since Moe is so weak in the Water.
Look, Water and water are two different things. He's sitting under a waterfall, full was water. The H2O kind. Nothing to do with Water, the metaphysical kind.
Pink imprints on the cloth.
This is frustrating. I'm going to chaulk it up to minor continuity/timeline issues. Bakker has some issues with time throughout, especially in TGO. There's no reason for there to be blood on the cloth, however I think the idea Bakker had was to show Moe proving to Kellhus he blinded himself. Granted, it should have been so long ago that unless the wounds are stigmata, they should be healed.
The incongruity with grasping the TTT as he had already been told he would grasp it.
Its not really incongruous in any way. He either really would have grasped it regardless of the foreknowledge, or its some total farce. Since TTT more/less worked out, its a pretty safe bet that its a real thing, so we can assume the hint was irrelevant.
This goes even weirder as the person who told him looks just like Kellhus and Moe (the Cish that zig-zagged to him),
A different question entirely. It is in fact very odd that this particular Cish looked like Moenghus. Was it wearing a blindfold? How could he even tell. No answers here on that one though.
kicking the skull ,
Foreshadowing almost certainly, but most likely foreshadowing either 'danger ahead' (lol jokes) and/or the death that occurs almost immediately afterward - ie Moenghus.
kellhus following a voice from nowhere to look about the place.
Internal monologue
Moe experimenting with Skinspies.
Kellhus was already doing this on the road. Why no Moe? Seems normal.
The whole meeting taking place at where Inri sejenus ascended.
Yes, an interesting bit.
Some answers from Moe "imperceptive slower" than others.
Lines up with dipping into the probablitliy trance. Standard dunyain stuff. Though makes me chuckle, if its imperceptible, then he shouldnt be noticing it.
Plus a few other things i've forgotten as this is from memory. I think this scene might have forshadowing if any scene is going to have it.
This scene, and all the others, especially if you stare at it too long.
I think we're well into
Epileptic Tree territory with this scene.
Aside, if someone comes up with a theory on why the thumb gleaming is important to the series, I'll gladly read about it

.
There was something about water coming out of Moe's eyes in that scene.
Edit: I can't look it up. I lent my copy of TTT to a friend.
Not Moe's eyes. He walks through the water coming from two eyes above him as he says "this is where the probability trance failed me"
There's also a bit about it looking like he's crying , IIRC. Its just water running down his face from the waterfall.