Earlier quoted context omitted.
I don't think generic tangents should be taken to include relevant tangents . I read this part of the guidelines (in context, with the surrounding language about flamebaits & tropes) as being about using something tangentially related as an excuse to pivot the conversation to your pet issue, not as forbidding you to add color to a conversation. That doesn't seem at all compatible with promoting curious conversation.…
I mean, they're table manners for a nerd messageboard so a lot more subjective than defamation law. You can always reverse engineer something out of them explaining the quality (or lack thereof) of some specific comment, after the fact. Less subjective are the effects and you can see them here - if a comment mostly produces corrections and rules lawyering, it's not a great comment and fills up the thread with meta an…
This is circular. I complained about this comment, therefore the comment is bad, and you can tell because I complained about it. I'd suggest it is the complaints that are noisy and should be avoided.
> To take an even broader view - if the goal of the forum is curious conversation, good toplevel comments have to look like invitations to curious conversation to others.
Anyone looking for something to nitpick and fight about will succeed. That can't be a motivation for guidelines because it's just a treadmill. My understanding is that one of the reasons the guidelines are so terse and loosely worded in the first place is to discourage rules lawyering. They aren't a book to throw at someone and say, "your comment is wrong, because you went on a tangent." (And I'm not really even convinced discussing defamation on a post about defamation should be considered a tangent.)