"It's really easy to become hyper-critical and respond to every idea with "yeah but that won't work because of x". This is lazy, don't do it."

I'd say that while this is true, there's an important "other side" to this, that not everything is a world-changing, ground-shaking idea that's going to revolutionize the way the world works. Sometimes ideas are indeed stupid, and one of the things I don't love about HN is the echo chamber effect. If everyone is telling you how great things are, coupled with 17 ("Constantly exaggerating how well you're doing can be very tiring.") things can disconnect from reality quickly.