Constantly? As if it were a psychological compulsion? So often that dang had to make a guideline about it, which no one even attempts to follow?

Two actually - the guideline against being "curmudgeonly" is separate from the guideline against going on a tilt because you get triggered by any website that doesn't look and act as much like plaintext as possible.

And yet if someone so much as cracks a joke they get rapped across the knuckles and lectured about a rule that doesn't actually exist (no humor allowed)?

Yes, that's negative. That's a culture of performative misanthropy.