If there's no rule, then what do you mean by "how the game is designed"? Surely, the design is to be found in the rules.
Emergence doesn't rely on explicitly written rules. They're things that
emerge from the game as designed.
I really can't simplify that. Emergent gameplay isn't written into the game because it fundamentally can't be; it wouldn't be emergent if it was.
I don't particularly try to speak them convincingly or with the naturalism of an actor.
Acting has nothing to do with anything I'm talking about. Referring to Improv =/= acting.
I believe the problem is a by-product of making such an assumption.
Ie the same thing Im saying. Its an
emergent problem resulting from the game's design centering almost entirely on task-based resolution which then interacts with the expectation of in-character improv being utilized during social interaction, which regardless of whether its explicitly written into the game or not,
is an endemic expectation of the hobby, whether one likes it or not.
This topic and the idea in the OP revolves around the premise of addressing the problem in a context that assumes doing both variants (improv + roll, as physical actions representing a combination of player and character skill) are both going to be and are desirable to have as part of the game.
I also don't know what you mean when you say they haven't been designed to be combined like that.
This was already explained in the OP. A failed roll making otherwise good improv pointless, not just in terms of invalidating player skill but also in depressing the desire to roleplay the interaction at all.
They combine by the player doing their roleplaying (which may include active roleplaying) and the DM possibly calling for an ability check to resolve the interaction.
That isn't the two ideas combining, you're just describing a procedure that puts one before the other.
There is no way to reconcile the simultaneous application of player skill and character skill in games like this that isn't either A) not using them simultaneously or B) making up houserules.
The games were not designed for this.
An ability check can be used to determine the outcome of the interaction
Which again has a high probability of conflicting with what was actually said.
It occurs to me that you don't seem to be picking up on the idea that the problem is in an emergent contradiction, where a person recognizes what they said would under no reasonable circumstance be the same thing as rolling a nat 1 or any other number that counts as a failure.
The point here is to eliminate the possibility of contradiction. Both are utilized simultaneously, and failure rests in the other person's reaction to what was said, which is mechanized through a combination of classic character skill mechanics and a new, independent system to grade improv and incorporate the numbers for both into a target number for the target to save against.
This by the way, more closely models in the broad strokes how real social interactions work.
One could be presenting an idea to fix a specific problem people have, and someone else on hearing their arguments could fundamentally reject their premise and never come around, and it doesn't even have to be because the person speaking is unskilled. It could just be because the other person just doesn't want to agree, and no amount of applied skill is going to change that.
Either way the outcome goes, it doesn't reflect on their attempts. Only they can decide if a lack of skill is the problem or not.
what reason would anyone at the table (including the player) have to believe that the player's speech was to blame for the failure?
Idk, considering that isn't the dynamic that was presented in the example nor any that Ive posted.