"Everybody just does the right thing" is not a solution you can implement in the real world.
> You keep describing it as a tactical error to use a strategy that amounts to hedging.
Maybe this is the source of the confusion: an intermediate score is not an optimal way to hedge. A hedge is a decision that offsets potential losses in the event of a bad outcome. No vote configuration on a single question can do that. It can, in some cases, reduce the chance of a bad outcome. In the best case, it does so by also reducing the chance of a good outcome (in favor of a moderate outcome). But crucually, each point affects each outcome in the same way as each other point.
So, by what rational reason am I choosing an intermediate value? Why would I prefer (in a contrived example, but all cases are linear) a 20% chance of both the good outcome and the bad outcome over both a 25% chance and a 15% chance? Moving from 4 points to 5 always does the same thing as moving from 5 to 6. It's linear, so the local maxima and minima are at the ends.
> There is no single "most important value".
You are making a linear probabilistic trade-off between two values. One of them must be more important than the other in order for any score assignment to be better than any other. Either being more important than the other will drive the score to one extreme.
> But why would you admit even this deficiency just to avoid allowing yourself to specify a score instead?
It's not something I want people to actually do. It's a reduction ad absurdum. Your approach does the same thing as a random approach, so - barring deception reasons - it must be a mistake.