Probably saying the obvious, but anyway:

What is the advantage of nice communication in a rationalist forum? Isn't the content of the message the only important thing?

Imagine a situation where many people, even highly intelligent, make the same mistake talking about some topic, because... well, I guess I shouldn't have to explain on this website what "cognitive bias" means... everyone here has read the Sequences, right? ;)

But one person happens to be a domain expert in an unusual domain, or happened to talk with a domain expert, or happened to read a book by a domain expert... and something clicked and they realized the mistake.

I think that at this moment the communication style on the website has a big impact on whether the person will come and share their insight with the rest of the website. Because it predicts the response they get. On a forum with a "snarky" debating culture, the predictable reaction is everyone making fun and not even considering the issue seriously, because that's simply how the debate is done there. Of course, predicting this reaction, the person is more likely to just avoid the whole topic, and discuss something else.

Of course -- yes, I can already predict the reactions this comment will inevitably get -- this has to be balanced against people saying stupid things, etc. Of course. I know already, okay? Thanks.