Why don't I see down arrows?
There are no down arrows on submissions. They only appear on comments after users reach a certain karma threshold.
A couple of years ago it went from 200 to 500. I was about at 180 at the time. The net result was that I kept searching for better material to submit and trying to improve my writing.
To put it another way, everyone is one good submission or ten good comments away from the threshold the day they create an account.
That's a bit too optimistic. My best comment has 36 points, yours has 58; your best submission has an impressive-yet-insufficient 291 points. 500 points is doable, but it's not trivial.
My point wasn't that it is trivial, but rather that 200 points or 500 points or 1000 points is obtainable and that the better one's contributions are, the more easily realistic karma goals may be met. Three hundred points seemed like a lot at the time, for a short time, then it was just another number - and I've probably lost that many points via downvotes.
I think it's around 500 - 1000 at the moment, I recall getting the downvote option around 500.