It's a per-instance setting. Downvotes just go into the void, here.
I also think it's a good idea. If downvotes were just used as a way for communities to self-moderate it might be nice, pushing things that are objectively not contributing anything valuable out of view. But in reality they're used as a disagree button at best, and in harmful ways at worst.
We just use the report button if something is truly out of place.