No matter the game genre, no matter the game story line or theme, that game's #1 responsibility is to the player. Lore exists to set up guidelines and rules for the player. Nothing more. In a game such as TES it's #1 responsibility is to me. Lore and story line are in deed important, but I disagree that they trump game play. At any time they may be bent or modified to enhance a player's experience.
That's not to say that I should be able to run around and do whatever I wish, story and lore be damned. On that point, clearly No.
However in this case, being able to (at some point) reforge deadric artifacts in some manner at higher levels as a reward for a certain achievement, my game play ultimately does trump lore. I site as an example face changing and perk resetting. Nothing in lore backing that up, yet it was implemented not on a lore basis but purely for the player's benefit. They didn't break lore doing so, nor did they break the game in any fashion.
Game play > Lore. Always.
The only time that it wouldn't be is when trumping lore breaks or destroys the game as a whole. For example, if I suddenly looted a Frag Grenade from a chest. Sure it would SWEET, but ultimately the presence of that grenade destroys the essence of what TES is all about.
This is only partially true.
Yes, the player is who Bethesda is building this game for (obviously). But they build it their way, suiting their lore. If fans like the games based around that lore, they buy them. If not, they don't. Therefore, Bethesda's sole responsibility is not to you. It's to the game itself. They build the game the way it is meant to be so that they can cater to the fans the actual game and its lore.
For the individuals who disagree with this lore (such as yourself), they release the construction kit so that those people can create their own experience that is noncanon and not truely in line with the lore. As I said, there's nothing wrong with this. It is your gameplay but it doesn't trump lore. It's you writing your own version of it.
Lore should always be above gameplay. That's the entire point of the game. If you don't like the lore (the rules) of a game/series, then you may want to play something else (or mod it to suit you). Instead of changing the lore to suit players, they should add new unexplored elements to the lore (which was done a lot in Skyrim), or find ways to work around it without breaking it.
Obviously, Betheada agrees with me on this to an extent, as they didn't allow the disenchanting of artifacts. The face changer and perk respec are bad examples as they didn't break lore, they simply added something new to it. The face changer clearly explained her presence and what she does. The perk respec is just another mysterious form of secret knowledge gained from Mora's Black Books.