Players can't fail a saving throw. They roll to see if the PC has failed. Saves are an in-game mechanic that only the PC can make or fail.
Huh? The saving throw is an event, involving the roll of a d20 looking to match or equal a target number, which occurs in the real world.
Within the fiction no roll is being made! Something like the following is taking place (Gygax's DMG, p 81):
A character under magical attack is in a stress situation, and his or her own will force reacts instinctively to protect the character by slightly altering the effects of the magical assault. This protection takes a slightly different form for each class of character. Magic-users understand spells, even on an unconscious level, and are able to slightly tamper with one so as to render it ineffective. Fighters withstand them through sheer defiance, while clerics create a small island of faith. Thieves find they are able to avoid a spell's full effects by quickness . . .
In the case of [MENTION=6801328]Elfcrusher[/MENTION]'s warlock, although the player's die roll is a failure in the fiction we imagine that the character's patron (i) protects her, and (ii) mandates that she maintain the ongoing deceit - which, in this case, means revealing whatever information the GM has given her player access to in virtue of the character having a 5 INT.
The outcome is thus the same as if the character knew nothing (due to a more typical characterisation of a 5 INT) and handed over all
that information under the compulsion of a ZoT.
His strength is his strength regardless of what he chooses to do. That he CAN do those things with his full strength is all that matters.
It may be all that matters to you, but it is largely irrelevant to [MENTION=205]TwoSix[/MENTION] or to me.
The function of stats in an RPG is not, in my view, to frame what the character can do. It is to frame what moves the
player is permitted to make, and to resolve those moves once made. In the case of TwoSix's 7 STR sorcerer, the upshot of STR checks will tend to be poor rather than good (because of the stat penalty), and TwoSix has already told us what, in the fiction, will be the explanation for that - namely, the character's withered arm.
I don't see how this is houseruling at all. Back in his DMG (p 15), Gygax observed that
The dexterity rating includes the following physical characteristics: hand-eye coordination, agility, reflex speed, precision, balance, and actual speed of movement in running. It would not be unreasonable to claim that a person with a low dexterity might well be quite agile, but have low reflex speed, poor precision, bad balance, and be slow of foot (but slippery in the grasp).
All TwoSix is doing is applying this idea to STR - his character is brawny, but with an enfeebled dominant arm.
And just as, in Gygax's example, having his/her PC be "slippery in the grasp" won't allow a player to avoid the adverse consequences of a low DEX, so in TwoSix's case being brawny won't allow avoiding the adverse consequences of a low STR. In both cases, it is the duty of the player (and to a lesser extent of the whole table) to ensure that the narration is consistent with the mechanical outcomes.