-snip-
Never said that length is similar to quality, that would be stupid of me!
But that a short answer can always be transformed into a longer one and you'll always have a better one.
Better in what sense if not in quality?
My answer is misleading you find?
Yes, there is no scrypt in bitcoin.
I'll learn something and the user asking the original question will have more elements. It's a win-win for me

And key presses are expensive in time. I'm pretty sure lots of sig spammer posting only 20 characters answers or even less do it only because they want to maximize profit. I find it a good way to counter them is to put a base characters limit.
I disagree.
I dont think you are correct.
I think your assumption is false and your conclusions are faulty.
None of these version costs me significant time to write. The thing that takes time is thinking about the answer and understanding your post. Neither is something you can enforce with requesting any number of symbols.
But you're right in the fact that contrary to captchas it does change the message. I just have the feeling it can't really change it in a bad way and can't think of a situation where it would be. Maybe I also lack imagination

If you cant see how a long chain words that say nothing is bad, I cant help you.