Why is leaking the reputation not good?

Herd mentality? E.g. Best Nodes gives this admonition:

By the way — Please don't upvote these nodes just because other monks thought they were good. If you do, their node reputations will increase — but then we won't really be showcasing the best nodes.

Next, "easily change back to the old behaviour." I check on PM, and sometimes comment on basic/mundane stuff, all without logging in. No, I cannot toggle that setting.

... newbies, who can't tell quality nodes from poorer answers.

One of the things I like about PM, is that you need to keep your brain in the ON position. Education is never easy, it involves some effort. I do wonder about your teaching career — did you consider your pupils as dummies who wouldn't know a difference unless told so?

A word about the quality of nodes... My earliest PM post was this, I think. The very first reply in that thread has a rep of +20, and I will tell you that it is a rotten, rotten piece of advice. If you're looking for one CPAN module that ought to be eradicated with kerosene, then that might it!

The pedagogically effective advice is generally highly rated though, I'll grant you that. But the rep mechanism is not up to the task. (The simplest example I can offer: say an old thread is followed up with a critical clarifying update. The first place you would check an old thread is at the end, for this very reason. But this node may get buried in the middle since nobody bothers to vote on it.)