I'm going to try to avoid discussing our discussion of the topic, and discuss the topic. I'm going to be unable to do that completely, because Hussar has used his last four posts to tell people what he thinks I've said rather than say what he actually thinks.
First let me talk about what I really think of the original example in some detail. The character used Dust of Disappearance to make a target invisible so as to avoid a gaze attack. This was supposed to be 'creative', and in a sense I suppose it is because its not the first order obvious use of Dust of Disappearance, but to me not only is it not particularly creative, nor suprising, but I rather think it shows a player who has gotten so invested in the rules that he's having problems being creative. I'd completely allow the usage without argument, but its not at all OP or even suprising. In fact, the main thing that is surprising about it is that the player didn't offer the proposition, "I close my eyes." Or, if he wanted to be completely safe about it, how about, "I cover my head with a sack.", or something of the sort. As a DM, I see all three propositions as being equally creative and equally allowable. I mean really all the player has done has made himself blind with respect to the basilisk, a trope and tactic that is as old as dirt. Tactically it might not even the correct thing to do depending on how effectively he can attack an invisible target and how effective an invisible basilisk is at attacking. Sometimes its a smart move. Sometimes its just trading one problem for another. It's balanced; but what really strikes me is that the player and the DM felt that there was novelty in turning a gaze attacker invisibile and never considered the completely outside of the rules proposition, "I close my eyes." There is in my opinion more evidence of creativity in the later.
Now, let's consider Hussar's example. First, let's get a few things out of the way. Hussar is wanting to insist that I want to block this move, and that I'm offended by it and putting unnecessary obstacles in the way. I've repeatedly insisted none of these are the case and in fact love the idea, but you notice that Hussar has admitted and repeatedly asserted that this plan's purpose was to change what the story was about. Moreover he's confessed that if his plan to change what the story is about is thwarted, he's going to get 'shirty with the DM'. He has repeatedly admitted that this tactic was to force the DM to handwave the travel through the desert. In other words, all his recent protests about how he wasn't trying to steal narrative authority from the DM don't hold water. We have a whole thread about him admitting to doing that very thing. Now note further, I noted that there were actions that a player could take that would short cut all travel through the desert, and that I was fine with them. So what is it that I'm upset about? It can't be that he found a creative way to get a desirable mount. I think that's great. It can't be that a player could short cut any plans I may have had for the desert, since I've already conceded that possibility. What's really troublesome about this is that having offered a plan he thought both foolproof and unbeatable (unless the DM cheats), and which further more he believed signaled that he didn't want to play in the desert, that not only must the DM respond to his proposition, "Ok, you make it across the desert without difficulty.", but if the DM responds in any other way, such as, "Ok, you begin riding the giant centipede across the desert. You find it rather difficult to hold on to its smooth chitinous back. Ahead you see the terrain becoming more rugged, and a steep wadi cuts across your immediate path to the north.", that the player is perfectly in the right to get 'Shirty' about it because the DM has ulterior motives and is cheating and is a jerk and so forth and so forth. My problem is precisely that that player has asserted virtually unlimited narrative authority, and is willing to go OOC and get angry about it to back up his claim to authority. And under those circumstances, I'm not going to DM.
But really, it's not because of the effectiveness of the plan. Tactically, his mount is not particularly effective at crossing the desert. A team of camels or horses would do just as well. Sure, he can go in a straight line using the beasts climb speed which might save some detours and allow bypassing some obstacles, but it just as easily could cause problems and at 40' speed its actually slower than many mounts. The ability to use forced march is nice, but you could accomplish that by just having spare mounts to go around and perhaps a willingness to ride them till they die, which you could manage by just spending a few gold peices before starting on your journey. Not being able to run out of mounts is nice, but not game breaking else mounts themselves would be game breaking. In other words, this situation is fundamentally within the capabilities of a party by third level or so. It shouldn't take a DM by suprise unless they are a novice. I don't really know what happened at that point, and we only have Hussar's point of view, but I've been in these situations enough - either as a DM or observing them as a player - to guess Hussar railroaded and bullied a DM by offering the DM outcomes disguised as propositions, by arguing the rules rather than playing the game, and well generally being 'shirty'. And that, not creativity, is what offends me. Well actually, that didn't offend me until Hussar directed his ire at me personally (check the thread timeline). And I readily concede that at some tables that's normal. I've seen tables that are dominated by this struggle for narrative control, each party fighting to have its outcomes imposed on the other and yet that group comes to meet every week, considers it normal, and even enjoys it.
There is this false 'either or' being offered, where you have "You turned my basilisk invisible? Fantastic! You skipped over my trek adventure?" is the opposite of the way I game and that to accept invisible basilisks and short cuts across deserts, you have to overturn the basic convention of "DM

layer relationship where the players tell the DM what they attempt and the DM tells them the results." I'm sure that Hussar is willing to explain exactly how that works. But I think that there is a very big difference between deliberately thwarting a player's plan and simply playing out the logical outcome of a plan and the details the plan. And well, if you conflate the two, and treat me merely for playing out your plans and propositions as me 'cheating' or trying to 'thwart you' or whatever, then I'm not going to DM. If you don't even want to play out the details arising from your own propositions, you don't need me at the table. You can call out propositions and announce the outcomes without me, because at that point I've been excluded from the game anyway. And if you want to play a nar game where the players call out bangs beyond the abilities on their character sheet and you want me to sit in the gamemaster chair, we are going to need a different ruleset that supports that sort of relationship equitably for all players at the table - story caller and protagonists alike.
Narrative control in D&D isn't the sole purview of the DM. The DM for example can't dictate to a player (normally) how the player plays his character or what choices he makes. He can't force a player to play a particular character, though he can set some hopefully broad and thoughtful guidelines. And the DM is expressedly granting narrative control to the players via the players ability to affect the environment through their characters abilities and actions. For example, the player has a reasonable expectation that if by the rules he does 30 damage to a monster with 20 hit points, that the narrative changes to one in which the monster or NPC is now dead (whether or not the monster was expected to be dead). So there are lots of means for player to express himself through play. In return the player concedes to the DM rights to create the setting, to play out the NPC's, and generally govern everything external to the player's character. The player can no more dictate outcomes to the DM, or settings to the DM, than the DM can tell the player what to do. All good DM's live with and embrace the reality that the players have enough narrative control within this relationship that they the DM aren't in control of the story. Nothing will ever go as planned, so it is better to not to get committed to much to a plan or to have plans that are so rigid that they break in response to a change.
So again, there is a false narrative being set up here. I am not thwarting the player who wants to conjure a giant centipede out of some failure to trust the player. On the contrary, I'm not thwarting them at all, but happily accepting there propostion and running with it. But, I would argue, that a player who thwarts the DM by announcing that the conjuring of a giant centipede leads to the logical outcome 'we get across the desert without playing through the journey' and who is essentially arguing for the viritually unlimited player right to set bangs and scene frame is failing to trust the DM. And that's as much as I want to talk about the discussion of the topic.