Note that the cited blog post has syntactically wrong code examples, which does not inspire confidence...

Can someone provide a more "official" view point (ruby core)?

Maybe this answer of the mentioned stackoverflow discussion does contribute to the trustworthiness, because it quotes the O'Reilly book "The Ruby Programming Language".

Great, that's exactly the kind of reference I had in mind :)

Here the quote from Flanagan/Matsumoto as given on stackoverflow:

[from 3.8.1: Object References]

When you pass an object to a method in Ruby, it is an object reference that is passed to the method. It is not the object itself, and it is not a reference to the reference to the object. Another way to say this is that method arguments are passed by value rather than by reference, but that the values passed are object references.

Because object references are passed to methods, methods can use those references to modify the underlying object. These modifications are then visible when the method returns.

@neumanrq wrote

Obviously this information causes some confusion. For example, the wikipedia article on evaluation strategies referenced the ruby-lang documentation as a proof that Ruby does use call-by-reference

I think you misunderstood the Wikipedia article. It clearly states that Ruby does not use "call by reference" but what they term "call by sharing" (i.e. call by value where the value is a reference); the paragraph you have cited only makes a statement about the used terminology:

However, the term "call by sharing" is not in common use; the terminology is inconsistent across different sources. For example, in the Java community, they say that Java is call by value, whereas in the Ruby community, they say that Ruby is call-by-reference, even though the two languages exhibit the same semantics.

I have no idea what the predominantly used terminology in the community is, though.

I think you misunderstood the Wikipedia article. It clearly states that Ruby does not use "call by reference" but what they term "call by sharing" (i.e. call by value where the value is a reference); the paragraph you have cited only makes a statement about the used terminology:

Oh, yes, you're right, my bad. I fully agree to the wikipedia article argumentation on call-by-sharing and the article points that out correct.

But the issue here remains: I still disagree to the statement

whereas in the Ruby community, they say that Ruby is call-by-reference

This statement was underlined by quoting ruby-lang documentation. That was the reason to make this proposal.

I fixed the wording due to your suggestion.