Guidelines for Personal Interactions

It’s a long list, but very comprehensive, good Job 👍 

I read that as assuming that you should always treat anything someone sends you as confidential, while not making the same assumption about what you send to others unless explicitly stated as such.

Well, yes, nevertheless it is a contradiction: either there is an expectation that others treat it as confidential, then no explicit statement should be needed, or it is not, then it should be needed. As it maybe unclear, what the expectation is, at least a rule (!) should show unambiguously what the legit expectation is. 

So these are not rules (indeed, it is called "guidelines"), but recommendations ... I would prefer something that is less ambiguous and thus closer to a rule, but of course I see that these guidelines just try to be practicable (and not normative ...) ... 

Yes, it's just a guideline for you to follow, without assuming that others will also do so.  Much of this it would not make sense for chess.com to enforce as a site-wide rule, and in some situations may not even be appropriate.

Indeed, that's the point ...

Ok