in the current system, the incentive is to downvote everything you don’t upvote to double your signal
For some reason, I don’t do that. The interesting comments I upvote, the few annoying ones I downvote, but half or more comments fall in the “meh” territory where I neither appreciate them, nor mind them, so I simply do not vote on those.
Not voting is not exactly halfway between an upvote and a downvote. Upvote costs you a click, downvote costs you a click, but no-vote costs nothing.
Sure, and that’s probably what almost all users do. But the situation is still perverse: the broken incentives of the system are fighting against your private incentive to not waste effort.
This kind of conflict is especially bad if people have different levels of the internal incentive, but also bad even they don’t, because on the margin it pushes everyone to act slightly against their preferences. (I don’t think this particular case is really so bad, but the more general phenomenon is and that’s what you get if you design systems with poor incentives)