What if the one who got the job heard that someone else is working in parallel on the same thing and has already made a lot of progress, such that if the one who got the job tells the people who hired him, they’ll stop the whole operation, and among other things he’ll lose the money. It’s almost certain that within another year they’ll know already and stop the whole thing anyway, but in the meantime he wants to keep working (for nothing) and get paid.

Then it’s obvious that he has to tell them. Returning a lost item.

Is that how you answer such dilemmas? At first glance there seems to be an unreasonably high moral bar here.
If a customer comes to buy shoes from me and I know that the store across the street sells the exact same shoes for half the price, do I have to send him there because of returning a lost item? And if he buys merchandise from me at the market price, and I know that the big competitor is about to break the market in another week and sell at a loss in order to block competitors, am I forbidden to sell to him? Something here sounds so unreasonable it’s almost absurd. Information is worth money, so why should I be obligated to hand out the information I have for free, especially when it hurts my own business?
The entire stock market is built on gaps in assessments (assessments are basically just information with a lower degree of certainty), and nobody has ever said that I have to disclose my analysts’ reports before every stock transaction and so on.

You’re mixing apples and oranges. You’re not supposed to disclose your analysts’ reports. What has to be disclosed is the relevant information. When we’re dealing with assessments, that isn’t information, and each person has to deal with that for himself. But if you have clear information, then in my opinion you definitely should disclose it.
Selling at a loss isn’t relevant here, because that’s a tactic that won’t last over time. I’m talking about a situation where there are different market prices.

If that is your Torah view, sir, then my own shocked and bewildered layman’s opinion is nullified. Did I understand correctly that in your view morality and Jewish law converge here in requiring disclosure?

Indeed, that is my Torah view, may its soul be bound up in the bond of life.
But as for morality and Jewish law, I stated my moral view. Halakhically, I don’t think anything here is firmly settled. There is room for the claim that where Jewish law is open-ended, morality is what decides. And perhaps morality and common sense also determine a halakhic category here (within the laws of returning a lost item).

What determines things in situations like these is the principle of measure for measure.
If that same So-and-so would have recommended Anonymous in the opposite case, then yes.
One should be fair and recommend So-and-so.
And if not, then not.

This principle should also be applied toward the employer. Would the employer have recommended Anonymous to write a book if he knew that Anonymous was better than him? If so, then one should behave toward him in the same way.

Usually the answer is no. A person takes care of his own household first, and only afterward of others.

Decisor, why does your fairness consideration apply toward the other candidate and not toward the one paying? The other candidate may perhaps find another job; the one who loses out here in the story is the person paying Anonymous.

Because the employer isn’t fair.
A fair employer should have paid Anonymous the full difference in profit created by the fact that he referred So-and-so to him. And the employer would then have benefited from a higher-quality publication.