They're a large part of why I've almost entirely stopped reading comments on HN. Too many people more interested in being right than having an actual discussion.

For both, it creates an annoying, pedantic atmosphere.

agreed.

in a 3 person private conversation, a factual inaccuracy that is not central to the point isn't going to harm the participants. Online, the conversation is public. People who don't know what they're talking about should be politely called out before they stir up FUD or otherwise cause harm.

(i am a hackerschool alum)

I think the focus is on pedantic corrections that are entirely irrelevant to the discussion and serve only to make the commenter feel superior. For example, see this recent thread [1].

The first commenter proposes a device that would use a Molex connector. The second points out that the device needs to interface with a wire not found on the Molex 8981 connector, a useful correction. The third makes the inane observation that Molex the company makes many connectors, when it is obvious that the first two commenters were referring to the Molex 8981 connector specifically.

[1] https://news.ycombinator.com/item?id=5638420