While some of the SO practices can feel dumb, I wonder what is the tradeoff we are making here? Could it be that for whatever reason (e.g. personality) we might benefit from accepting these "dumb" choices because it also brings with it unrelated benefits? For example, might it be that if they were forced to accept "frivolous" statements such as "thank you" (from the example you gave), might it cause moderators to not moderate, and thereby allow in spam & other nasty bits?

It is worth bearing in mind that if we, "good people", complain about moderation, we only see the parts of it that touch our "good posting". There might be plenty of good that moderators are also doing, which only the bad guys see.