Some readers may take you a little more seriously if you have very high karma, or a little less seriously if you have very low karma.
In practice, though, if you have very high karma then the chances are that you're active enough that those readers will recognize you and form whatever opinions they do more on the basis of experience than of your karma score, and the state of having very low karma doesn't tend to persist very long: someone who posts things other LW participants like will soon not have very low karma, and someone who doesn't will usually notice and give up. (Or improve.)
I have to click through to your user page to look at your karma score; do a statistically significant fraction of readers check karma before evaluating a post?
How do you gather a theory of Counterfactuals, Karma, and Economics, into a revised algorithm for thinking about Lesswrong?
Thinking of Karma as money.
There are a lot of things that one may consider worth saying on Lesswrong. Things that go against the agenda, things that may make people unconfortable, things that are different from what the high-ranking officials would prefer to read here. But we don't do it, because we don't want to "loose" precious Karma points. Each Karma point loss is felt as an insecurity, as a tiny arrow penetrating the chest. But should it be that way?
Here is the alternative: Think of Karma as money. You work hard for getting a few karma points by writing interesting stuff on superintelligence and whatnot, society rewards you by paying some karma points. Then you go there and write something you think people need to hear, but will downvote for sure, at least initially. Some people by now will be very rich, which affords them the opportunity of saying a lot of things that they are not sure will get themselves upvoted, but are sure should be posted.
Citizen: Wait, you said counterfactuals...
Yes, just like your State doesn't really care or like you going out in your hovercraft through the river and using equipment to climb a mountain, so the people here may not care about putting attention into that idea which you think they should hear. Thus, they dowvote it. They make you pay for their attention. If you mentalize it as "they are drawing my soul and life is worthless if karma is negative", then you are much less likely to end up posting something controversial that may be counterfactually relevant.
Just like efficient charity donation works because the vast majority of people are not paying to effectively cause others into being happier, using karma as money works because the vast majority of people are afraid their soul is being sucked every time a downvote comes. But it isn't, this is just the price people charge for their attention, if you think the way I'm tentatively suggesting. It is just a test worth trying, not necessarily something that I fully endorse. I like the idea, and have been using it since forever. Every post linked here, or an earlier subpart of it, has been negative at some point, and from before posting, I knew it would be a "costly one". Try it, if you are rich, you may have nothing much to loose, and more controversial but useful stuff will show up with time.
Let's see how much this costs.