I consider my role to be a cop, not a lawgiver. Describing forum ethics is not a part of my job. We already have tools to enforce the things you said: if someone writes stupid comments, spoilers, or trolling comments, anyone can downvote them. My superpowers will be needed if someone starts abusing these tools, e.g. by mass downvoting, because that's what other users cannot investigate.

What I said is orthogonal to whether having explicit debate about forum ethics is good or bad. I can imagine it going either way. I think most people would agree with the examples you gave here. Anyone should feel equally free to initate this kind of debate, and my opinion should have no special weight there. Opinions of people from MIRI or CFAR should have extra weight, I think, but I am not in that set.