The problem is that what makes 'sense' to one person may not make sense to another. One explanation to justify a conclusion may be unsatisfactory to another person. There may be many possible causes for a given effect.
It is indeed a problem when that happens.
Different lines of reasoning based on common information may result in more than one 'sensible' conclusion which are both logical and contradictory.
Which ones should a person choose?
Which person? If it's Marc Miller or one of his minions, the person should choose one and stick to it. I might personally prefer one solution to the other, but as long as one of them is chosen, I'm content.
Each will choose different explanations and thus argue relentlessly about it, even over decades.
That depends on the kind of controversy. If canon says a+b=10 (for a and b being positive intergers), then there are several equally valid solutions. But a = 15 isn't one of them, and neither is a = 8, b = 7. And only one of those equally valid solutions can be true for any single universe. And the OTU, as the definite article indicates, is a single universe.
Sometimes disagreements are perfectly reasonable. If you want a to be 2, you'd valiantly oppose any attemt to define b as anything other than 8. That's when a person with the authority to do so should step in and make a decision.
But some disagreements are not reasonable. The sort of arguments that annoy me are the kind where you have several canonical statements that can't all be true at the same time, like:
a+b = 10
a = 8
b = 7
All to often, one side will point out that canon says that a = 8, so that MUST be true while the other will point out that canon says that b = 7, so that MUST be true. And when someone proposes that 'a+b=10' be changed to 'a+b=15', a third person has a fit.
Also, when changing an inconsistency in canon, the more pervasive that bit of canon is, the greater the follow-on chains of inconsistencies and broken canon there will be.
That's certainly something to take into consideration.
People should work to mold their TU to fit the canon background as they prefer instead than seeking to mold the OTU to fit their own private TU.
Why? What do you believe the point of having an OTU is?
I can't help but wonder if excessively aggressive nit-picking might drive away potential players who don't care about that stuff.
We'll just have to keep pointing out that they're not obliged to pay any attention to excessively aggresssive nit-picking, won't we? Or even to judiciously unaggressive nit-picking if it bothers them.
Hans