Because it's Paul Graham, who's a very rich and wise venture capitalist, over whose musings people who also want to be very rich and wise venture capitalists someday, must fawn and nod their heads and agree with, as if he has said something very profound.

Is this tweet wise and profound? Obviously not. Is there a kernel of useful information buried in there? Barely. As you said, is the purpose really just to elicit a reaction? Obviously, yes.

These kinds of remarks remind me of people who used to brag about getting good grades despite not doing the reading or homework, as if that's a virtue.

They're not harmless, because plenty of people will take away from this the idea that you don't need to do research on things, in general. Because Paul Graham is very rich and wise and he said so.

It's dumb fortune cookie wisdom, like so many of his wise and profound edgy, contrarian viewpoints.

Actually small business advisors insist that founders do need a detailed business plan. But it's both necessary for founders, people giving advise and everyone involved that it depends on the kind of business. I used to think business plans are old school and overly formal. But it's good to know the correct reason.

To inform potential applicants to YC or other founders that business plans are not essential/important to raise investment?

It might be something to point to if a startup talks to an angel investor who insists on seeing such documents.