Anyone can file a plagiarism lawsuit and claim an author stole their idea, even if it has no merit.
No, they can't, because plagiarism is, in the most literal sense, not a crime. There cannot be a lawsuit alleging a civil or criminal violation of plagiarism, anymore than there can be a lawsuit alleging you wrongfully looked at the moon. The lawsuits you're talking about are accusations of copyright infringement. You can call it plagiarism colloquially, but the legal mechanism at work is copyright (or patent, or trademark).
The reason it's a terrible analogy for what you're talking about is that we don't want to take other people's ideas, which is why the board was kind enough to institute a rule against posting story ideas in the Trek Lit forum frequented by authors -- although that's really in the board's interest too, because if that rule weren't there, we'd have to avoid this forum, and the participation of pro authors and editors in the forum is one of its major draws.
I imagine most of the artists I'm talking about aren't twirling their mustaches at defrauding IDW by passing off bootleg starship pictures as their own work with the help of Google Image Search, but just have a poor understanding of copyright, trademark, and the legal/ethical importance of the provenance of their reference material. Illustrators are just a bunch of cowboys living by the seat of their pants, or sometimes really lazy. Clearly, no one has yet put the fear of God into them with regard to intellectual property, unlike novelists and screenwriters.
I really don't see what that has to do with a policy meant to protect authors from exposure to the risk of unfounded plagiarism lawsuits. After all, a work is only copyrighted if it's actually created and published in some way. Posting a suggested story premise on a BBS doesn't count. So what you're talking about is a different matter entirely. You're comparing apples and oranges.
As I said earlier, under U.S. law, neither publication or registration is required for a work to be protected by copyright, it's legally an innate property of any work of creative expression done in a fixed, duplicatable form. Napkin doodles have a copyright. A note with a little poem telling your spouse you had to leave for work early has a copyright. The posts you make on this board absolutely have a copyright, and posting them
is a form of publication; if someone collected all your posts and put them into a print-on-demand book on Amazon, that would be an infringement on your copyright, and you could sue them for that (but not for plagiarism, because that's not an issue the law deals with). We've even made a tiny little publishing agreement with the board when we registered, it's right down at the bottom of every page for reference, under "Terms and Rules:"
You are granting us with a non-exclusive, permanent, irrevocable, unlimited license to use, publish, or re-publish your Content in connection with the Service. You retain copyright over the Content.
If someone posts "Let's have an episode where Kirk and McCoy have a magic picnic like
Alice in Wonderland," and then you write "Shore Leave," and they sue you, their lawsuit is literally that you infringed on their copyright for the exact series of words, "Let's have an episode where Kirk and McCoy have a magic picnic like
Alice in Wonderland." It doesn't matter if one is a sentence and one is an episode, any more than sheer length would make it not copyright infringement if I published fifty novels based on
Firefly that added up to a hundred times the content of the TV show. "Plagiarism," "premise," "story ideas," those are all informal terms to make the concepts clearer without getting into the exact mechanical workings of why some things are legal and some things are crimes (or civil violations).
The upshot, once again, is that the same legal framework that allows someone (rightly or wrongly) to sue over copyright infringement if a story similar to something they posted where the author could've seen it is published
should allow someone whose fan art was traced in a comic to sue over copyright infringement, but as far as I know, there has yet to have been a high-profile case setting that example publicly. There have been several low-profile cases which were handled informally that I know about, usually with the removal of the infringing artwork from or the addition of a credit in future editions, or just went nowhere, but nothing that created as much pain as cancelling a novel or script that was in production (so, nothing that would make artists wary of being accused of infringement the way writers are).
It's ironic, because there's actually much less ambiguity when fan-art is used in official products. Two different people can plausibly both independently have the idea for the premise "Kirk and McCoy have a magic picnic," but it's a lot more of a stretch to argue that two people can independently create the same exact picture of the U.S.S.
Enterprise, from the exact same angle, the highlights and shadows in the exact same spots, the weathering and paneling in the exact same patterns, and so on. Never mind when the infringing official production uses an image of a fan-made design that isn't closely modeled on something from the original property, like old pictures of Koener's
Enterprise popping up in official contexts.
