you don't need to downmod; you just need to be relatively worse. what happens to new users you ask? that's dealt with by another method; sticks out tongue.
but i think downmodding looks like something tacked on as an afterthought, being an opposite of "upmodding." when you're broke, you don't have money. when you're in debt, you still don't have money. if some comment is modded -3, it's bad. -50 is bad too. but you don't really care that one is 47 more bad than the other. while there is a case for, say, making a severly bad comment that just takes away all your credibility, first of all it's unlikely that would be the doing of a sane user, and thus the second, such a user is probably something of a troll; if your service is open-registration, there's nothing to prevent said troll from registering again, receiving zero credit, essentially excusing themselves of all debt. it just violates common sense.
i would go on but i'm teetering right now. in conclusion, abolish downmodding.