I've been thinking about the apparent split between player and character over the last couple of days, trying to formulate my thoughts. I'm not quite there yet, but here goes all the same...
At the end of the day I believe that the distinction between player and character is largely a false distinction. As far as the non-mechanical, non-rules related issues go, there is no difference at all. There is just the player. The character doesn't actually exist as an independent entity - it's just a depiction of ideas and concepts rattling around inside the player's head.
A player modifies his usual behaviour and attitudes to match his conception of his character (in other words, he "role-plays" the character) but it's still just the player at the end of the day. Rules mechanics and systems can give the character powers, knowledge and insight that the player does not possess, like fireball spells, arcane insight or a roll of 20 on a Search check. The player can roleplay a character who is less intelligent, less wise or less charismatic than himself - not not more intelligent, wise or charismatic. In order to represent greater levels of mental or social acuity (and for any physical actions), the mechanics take over.
So, when you ask "does the ToH challenge the player or the character?" what you are really asking is whether the ToH challenges the player or the mechanics of his character? The player can always "play dumb", but that's still the player's decision, and hence his own capablities that are being tested.
The idea that in the olde dayes, the player was challenged, but these days it is the roleplayed character that is challenged is, imho, patently false. In both cases, the Tomb challenges the player and the mechanics of his character. The non-existence of the character as a separate identity makes anything else impossible.
(You might wish to ask whether people roleplay their characters more these days than they did 30 years ago, but that is a separate issue and wholly unrelated to the ToH).
So the ToH challenges the reasoning power of the player (portrayed through his character or not) when he stands before the throne in the many-pillared hall. What will he do with the sceptre and the crown? It challenges the mechanics of his character when he looks for the secret door in the throne. Will he roll high enough on his Search check? (Or his find secret doors roll, if you are playing 1e). And, it should be noted, this not specific to the Tomb. It's how D&D works.
As an aside, I'd also dispute a blanket generalisation that the ToH cannot be reasoned through by player or character. I saw it happen last week. My players used their own reasoning, but they also roleplayed their character's reactions when these might differ from their own (see Alma's actions with the rope at the 100' deep pit). They figured out the symbolic connection between the gold crown on the throne, the silver image below it and the two ends of the sceptre. And they also succeeded (or failed) when it came to the mechanics of their characters, either through skill checks, combat rolls or saving throws (and in the latter case, it was the characters, not the players who were ultimately challenged and defeated by Acererak's soul drain - it was an issue of mechanics that led to those failed saves and had nothing at all to do with the actions of the players).
Just some thoughts. Apologies for rambling

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