In situation 1, I would allow a player to earn one check by having a -1D, but I would discourage having a player earn two checks by giving +2D. I would hold this stance; because, it seems to me, they are arguing things that should matter for both sides. If a side were flawed enough that it gives +2D to an opposing side, that seems like the opposed side should win without a test; I guess I mean, it seems less pitched in that narrative. However, in the case of having -1D, it seems to me that’s more closely linked with a personal trait impeding a character making a solid point. It feels easier to maintain a pitched scene.
In response to such a scene, I would say the player who initiates the issue (plaintiff) is at risk of condition/twist outcome, but the player who stands to oppose the matter (opposition) is not at risk. So, the plaintiff makes the case, tolerates perhaps a personal trait creating a flaw in the argument, and risks Success w/ Condition or Twist. This means also, the plaintiff will not be swayed; as in, the opposition cannot have Success w/ Condition; if they roll cowards, they simply fail to get what they want (possibly are swayed to a new line of thinking) and play continues. If the opposition rolls successes while the plaintiff rolls cowards, the plaintiff gets Success w/ Condition or Twist.
In case of a Twist, perhaps no side is swayed, and an entirely other scenario presents that must be dealt with before a consideration of the issue can continue later.
So, it’s a bit complex, and I’d lean against allowing a player to ‘throw’ the test by giving +2D. That’s just me; I won’t argue it’s wrong or fails to meet the spirit of the rules.
In scene 2, I would insist on Instructor. I simply would. I see it as one patrol mate has a reason to train (sparring is training, fighting is fighting). If there is a reason to offer training to a patrol mate or other mouse, or a reason to request training from a patrol mate or other mouse, that’s a clear Instructor test.
So, let’s imagine it is a Tenderpaw requesting training from a Mentor. In that case, the check must be spent by the Mentor to offer Instructor-tested sparring (although another patrol mate could serve as Helper as well). In that case, the Tenderpaw still has a check and needs to consider how to recompense the Mentor spending a check on training.
So, let’s imagine it is a Patrol Guard offering tips and practice for a Guardmouse patrol mate. In that case, the check is spent by the Patrol Guard (presuming they discuss and agree–no need to waste a check if the Guardmouse doesn’t want to), and the Guardmouse joins without spending a check.
In both examples above, both characters have tests to make, one side is making an Instructor test while the other side is getting a pass/fail or a test (pg 246). I’d say the risk in Instructor is similar to other tests: Success w/ Condition(s) or Twist. Perhaps the risk is becoming Injured while sparring. But, in both examples, the mouse gaining training is not at risk; they simply get one of the results.
I would hold this stance; because, I would not offer a Fighter Vs Fighter unless there is clearly something to fight over. If either side is merely interested in practice and advancement, the Instructor skill is the correct choice. If both sides are equally matched in Fighter, neither has traction for teaching something new to their patrol mate; having another patrol mate assist would be required to tip the scales toward teaching or coaching something worthwhile. So, in that way, I would still place constraints on Instructor.
If players still want to spar at the end of all that, and want to form a scene in which they are risking Injured state or other results, I’d say it doesn’t fit unless they have a good story to tell why they are dueling in the patrol. That’s not impossible! They can create problems internally leading to brawling and more, yet I would insist they have to create that narrative first–rather than after the test.
As for player-suggested tests or player-Vs-player tests breaking the game. I think not. I think that’s a great element of player authorship. I just insist that if they are going to suggest reasons to oppose one another, it needs to have dramatic meaning, not simply a mechanical outcome. (That scene 2 is simply a desire for both players to gain a pass/fail in Fighter rather than drive a dramatic story of internal conflict.)
TL;DR: Scene 1 works as long as there is one patrol mate acting as plaintiff and another or more acting as opposition; in that case, plaintiff wins (possibly with Condition) or a Twist derails the argument; opposition risks much less in the outcome and cannot win-over their patrol mate. Scene 2 is either a passionate, dramatic fight over something actually present in the narrative, or RAW indicate it is an Instructor test from a patrol mate for one or more other patrol mates or mice; the mouse teaching or coaching is at risk, and the learner(s) are at no risk; however, both gain pass/fail in the scene.