I originally wrote this as a comment on a post which had negative net karma when I first saw it. I figure what I wrote is worth also posting to the top level, so that it can have more chance to be seen and thought about
When I came upon this post, it had a negative karma score. I don't think it's good form to have posts receiving negative net karma (except in extreme cases), so I upvoted to provide this with a positive net karma.
It is unpleasant for an author when they receive a negative karma score on a post which they spent time and effort to make (even when that effort was relatively small), much more so than receiving no karma beyond the starting score. This makes the author less likely to post again in the future, which prevents communication of ideas, and keeps the author from getting better at writing. In particular this creates a risk of LessWrong becoming more like a bubble chamber (which I don't think is desirable), and makes the community less likely to hear valuable ideas that go against the grain of the local culture.
A writer who is encouraged to write more will become more clear in their communication, as well as in their thoughts. And they will also get more used to the particular expectations of the culture of LessWrong- norms that have good reason to exist, but which also go against some people's intuitions or what has worked well for them in other, more "normie" contexts.
Karma serves as a valuable signal to authors about the extent to which they are doing a good job of writing clearly about interesting topics in a way that provides value to members of the community, but the range of positive integers provides enough signal. There isn't much lost in excluding the negative range (except in extreme cases).
Let's be nice to people who are still figuring writing out, I encourage you to refrain from downvoting them into negative karma.
I don't really agree with this. Sure, some people are going to write stuff that's not very good, but that doesn't mean that we have to go overboard on negative feedback, or be stingy with positive feedback.
Humans are animals which learn by reinforcement learning, and the lesson they learn when punished is often "stay away from the thing / person / group that gave the punishment", much more strongly than "don't do the thing that made that person / thing / group punish me".
Wheras when they are rewarded, the lesson is "seek out the circumstances / context that let me be rewarded (and also do the thing that will make it reward me)". Nobody is born writing amazingly, they have to learn it over time, and it comes more naturally to some, less to others.
I don't want bad writers (who are otherwise intelligent and intellectually engaged, which describes almost everybody who posts on LW) to learn the lesson "stay away from LW". I want them to receive encouragement (mostly in forms other than karma, e.g. encouraging comments, or inclusion in the community, etc.), leading them to be more motivated to figure out the norms of LW and the art of writing, and try again, with new learning and experience behind them.
It's not all that arbitrary. Besides the fact that it's one of the simplest numbers, which makes for an easy to remember / communicate heuristic (a great reason that isn't arbitrary), I actually think it's quite defensible as a threshold. If I write a post that has a +6 starting karma, and I see it drop down to 1 or 2 (or, yeah, -1), my thought is "that kinda sucked, but whatever, I'll learn from my mistake and do better next time".
But if I see it drop down to, say, -5 or -6, my thought starts to become "why am I even posting on this stupid website that's so full of anti-social jerks?". And then I have to talk myself down from deleting my account and removing LW and the associated community from my life.
(Not that I think LW is actually so full of jerks. There's a lot of lovable people here who talk about interesting things, and I believe in LW's raison d'etre, which is why I keep forcing myself to come back)