You are the one who introduced correctness into the argument. Alicorn said:

Do you expect anyone to benefit from your expertise if you can't convince them you have it?

Feel free to read this as 'convince them your expertise is "useful" ' rather than your assumed 'convince them your expertise is "correct" '.

The underlying point is that there is a very large amount of apparently useless advice out there, and many self-help techniques seem initially useful but then stop being useful. (as you are well aware since your theory claims to explain why it happens)

The problem is to convince someone to try your advice, you have to convince them that the (probability of it being useful * claimed benefit * probability of claim being correct) is greater than the opportunity cost of the expected effort to try it. Due to others in the self-help market, the prior for it being useful is very low, and the prior for the claimed benefits equaling the actual benefits is low.

You also are running into the prior that if someone is trying to sell you something, they are probably exaggerating its claims to make a sale. Dishonest salespeople spoil the sales possibilities for all the honest ones.

If you can convince someone with a higher standing in the community than you to test your advice and comment on the results of their test, you can raise individual's probability expectations about the usefulness (or correctness) of your advice, and hence help more people than you otherwise would have.

P.S. I did go to your site and get added to your mailing list. However, even if your techniques turn out positively for me, I don't think I have any higher standing in this community than you do, so I doubt my results will hold much weight with this group.

You are certainly right that "one does not have to be convinced of the correctness of something in order to test it." But as you also said, immediately prior, "Either someone uses the information I give or they don't."

If we test information that we do not have reason to believe is useful, then we have a massive search space to cover. Much of the point of LW is to suggest useful regions for search, based on previous data.

So no, correctness is not a necessary condition of usefulness. But things that are correct are usually rather useful, and things that are not correct are less so. To the extent that you or your expertise are reliable indicators of the quality of your information, they help evaluate the probability of your information being useful, and hence the expected benefit of testing it.

Perhaps some parties on LW are actually confused by the distinction between truth and utility. I do not suspect Vladimir_Nesov is one of them.

Actions of high utility are useful. Of a set of available actions, the correct action to select is the most useful one. A correct statement is one expressing the truth, or probabilistically, an event of high probability. In this sense, a correct choice of action is one of which it is a correct statement to say that it is the most useful one.

It's beside the point actually, since you haven't shown that your info is either useful or correct.