This is what I’m asking for, specific legal cases covering forums. Someone will challenge their copyright ownership (the correct term in the USA and not related to “copywriting”). NOTE: I’m not inviting an off-topic discussion of the comparison of legal systems because the legal details will be in the case record if we can find one. I’m just asking if there have been any formal challenges reviewed by copyright and intellectual property specialists. (In the USA there is a separate legal system and court set up to handle intellectual property cases like copyrights and patents.)
There may actually be room for a full legal case. The European “Right to Be Forgotten” and other rulings on privacy laws came from individuals insisting on their rights. The EU’s “Right to Be Forgotten” was formally established by a man in Spain demanding that references to his past financial problems be removed from internet access. This right is based on a law that was already in place. Google was ordered to follow that law and Google asked the Court to decide if the law was being correctly applied. I’m asking if a case has been heard and a decision issued.
In the USA, the purpose of the copyright, patent, and other intellectual property laws is to encourage creation of intellectual and artistic content. You can hire me to fly to a location and make a painting, pay for all of the materials AND travel/living expenses and I still own the painting. Even if I give it to you or sell it to you, you can have posession rights and “use rights” but only to display it (or not) and you may not alter the painting to turn it into a different work (like add a mustache to a portrait 
) unless we have a contract that uses specific recognized terms to transfer full ownership of the intellectual property (the painting) to you. [1]
In some cases, a writer’s contract with a publisher has been canceled because their work turned out to be far more valuable then the publisher or writer thought it would be. The U.S. system heavily favors the creator. I would expect this preferential treatment to also apply to “public” forums. The copyright law I referred to above includes a famous case about a statue that was contracted specifically for public display. The artist retained full ownership and control over the creative content of the statue while the client retained possession and physical control of it.
This depends on how creative the post is. It’s very easy to say what should be–especially on the internet ( 
)–but establishing a legal reality requires more than even broad agreement, no matter how “obvious” the principle might be. Anyone can discuss and speculate and even loudly declare the principles involved. We may even have wonderful insights into how things should be. The way that modern societies resolve questions like ownership of work output and other broad social questions, though, is through [1] law and [2] court review. In short, our individual opinions don’t mean as much as we might like them to, even if those opinions are brilliant. We can only hope that the legal specialists are as bright as we are. 
These discussions have been goin on a very long time now and probably started in the 1970’s when the Internet was first put into working form. Bulletin board systems from the 80’s would also have these copyright situations. Meta.discourse.org has a topic on it from 2013. Because we’ve been using forums for so long now, I would expect some formal review and decisions about individual copyright of forum posts. The ability of Terms of Use to force users to transfer their copyright ownership could be limited. These discussions have been
going on for along time, so surely some court somewhere has looked at the question.
I’m an inventor and have studied the applicable U.S. law, including a Harvard Law School online course and retain two patent/IP attorneys but if I ask them this question they’ll charge me a handsome fee for doing research or writing up their knowledge. I also doubt that they know about publishing in a forum. ↩︎