Dan is right in the sense that linear voting has issues. But he's wrong in that quadratic voting also has issues. Neither is a very good but until someone comes up with a better idea we're stuck with one or the other and thus far the devs have chosen to continue supporting linear as the least bad (in their opinion) option.
BTW, @mattclarke the problem with downvoting is much the same now with linear as it was with quadratic: For the most part nobody does it, and therefore whenever anyone does, it becomes a Huge Big Deal, personal attack, starting a war, throwing old ladies down the stairs, etc. If downvoting were much more common and not a Huge Big Deal, a lot of things about this platform would work much better. I don't know how to get there.