I currently need 413 more points to downvote at all.

So how many downvotes did you use when your karma was still highly positive? That's likely a major part of that result.

But what a way to discuss this: "high number." If this is supposed to be a community forum, why doesn't the community even know the number--or even care.

The main points of the limit are 1) to prevent easy gaming of the system and 2) to prevent trolls and the like from going though and downvoting to a level that doesn't actually reflect communal norms. In practice, 1 and 2 are pretty successful and most of the community doesn't see much danger in the system. That you can't downvote I think would be seen by many as a feature rather than a bug. So they don't have much need to care because the system at least at a glance seems to be working, and we don't like to waste that much time thinking about the karma system.