your current reading comprehension needs a boost. If you look back, you'll see that the current discussion from my comment is about a hypothetical world where today's copyright laws have been repealed
OK, let's do that. Note: I'll avoid quotations to keep the length down.
In reply 86, you said that copyright laws simply made a particular contract the default. (This suggested that something similar to copyright could be implemented in a non-copyright legal system.)
In reply 88, I pointed out a fundamental error in that position: copyright binds third parties who are not parties to any contract. Contracts cannot be used to do that. (myrkul999 had said something similar in reply 87.) I then gave a simple example of how a situation would be handled differently with copyright and without.
In reply 89, you disagreed with something in my example, but did not explain whether you disagreed with the copyright part or the non-copyright part or both. The rest of the post is about conditions under current copyright law. The normal interpretation for any reader is to assume that the first sentence of a paragraph ties in with the rest of the paragraph (unless the writer specifies otherwise). The part of the paragraph that was clearly about copyright talked about fraud. (It did not discuss the main point--the binding of third parties under copyright.)
In reply 91, I asked why you added the extraneous matter of fraud to the example. When discussing today's (copyright) law, it was clearly stated.
In reply 92, Andreas discussed selling under copyright, again with the extraneous matter of fraud. (It also contained a claim about current copyright law.)
In reply 93, I showed that Wikipedia said that that claim (about current copyright law) was false. I asked again why fraud was introduced.
In reply 94, Andreas again argues the extraneous matter of fraud, not stating whether it applies to the copyright case, the non-copyright case, or both. Since the previous several posts had been primarily or entirely about copyright, I think it reasonable to assume either the copyright case or both cases. YMMV
In reply 96, Andreas said "what you said (that A can sue C directly)", which was what I said happened under current copyright law.
In reply 97, I quoted that section, continuing the discussion about current copyright law.
In reply 98, Andreas talked about copyright.
I'm pretty sure that that's an accurate summary. Many of the posts were explicitly about copyright, and most of the rest clearly distinguished the copyright case from the non-copyright case. Are you sure it's my reading comprehension that needs a boost?
there are no current "IP" laws, only trademark, copyright, and patent law
It is my understanding that, in addition to those, trade secret law is considered IP law.