>>796078I'm more addressing the crux of what you said, because it is often used by people to dismiss anyone who wishes to discuss the transparency of chuubas.
"If they do it long enough, you should just assume they are being completely sincere and true to themselves". First of all, that is in the first place very dubious statement. Saying that a certain mask couldn't possibly be more or less artificial than other masks is something I would heavily contest.
But even if that were to be agreed upon, it still leaves one open to wish to see multiple masks, and thus getting a fuller image of the chuuba. If one mask says something, and other mask would say something else, only by knowing both, does one get a bigger understanding of the character. Thus a certain meaning of sincerity could still be discussed, by comparing the answers of different masks.