Having made (what I thought were polite) comments on Reddit only to get down-voted into oblivion, I agree that HN has one of the most thoughtful and respectful communities I've participated in.
In my experience, it's pretty easy to misjudge the expected overall level and style of politeness in a given social space. Many people were raised with the idea of politeness being a safe default, but in some spaces being too polite can come off as aloof or condescending.
There have been a number of HN threads that have become quite, er, hostile or toxic in the past. The most recent example of this would the comment thread for this article: "Richard M. Stallman resigns" (https://news.ycombinator.com/item?id=20990583)
HN has a lot of smart people. People don't like being fact checked, especially when they believe they discovered something significant until experts show it was a basic misunderstanding.
This is the cannonical example of why HN gets it wrong. You really are not an expert in 99.99% of the topics on HN, so having this kind of holier than thou attitude is just really obnoxious.
And this is the canonical example of why Twitter gets it wrong :)
I'm not talking about myself. Never even remotely implied it.
HN is filled with the 0.1% that truly are experts on individual topics. You'll find people that wrote papers on quantum mechanics chiming in on QM discussions, people with decades of RF HW experience correcting those 5Ghz conspiracies, start-up founders jumping in on discussions, and (in this case) people that can read spec sheets and understand how systems like these are built and programmed.
No one's an expert on much, but plenty are experts on something. Twitter's often too shallow to even entertain the possibility of being wrong.