Blink. Ooo-kay, so this explains why my karma total jumped from roughly 970 to 4026. I thought I was seeing a bug. I'm not sure if I'd have made top-level posts quite this valuable - I'd probably have picked a 5x multiplier or so - but at least this certainly encourages me to write more top-level posts. Thanks for implementing my suggestion!

And yes, there is something silly about being motivated by an abstract number on a small-ish community site, but I can't help my ancestral status-driven urges.