> the exchange of emails and payment sound like some kind of contract
Beware that this is very dependent on jurisdiction. There are places where such informal agreements are completely non binding. IP laws vary quite a lot as well. So your intuition might be completely wrong. Just sorting this out would be a nightmare (the author was working in Germany for a Swedish company; which law should apply? Then there is Microsoft).
> If Microsoft replace the poem, I'm not sure anyone would notice except the author wouldn't have a fun fact for his bio.
He would still have it: this happened and whatever happens next won’t make it un-happen retroactively.
Well, Microsoft's legal team obviously came to the conclusion that the emails and payment were at least sufficient to grant Mojang a license to the artist's work. So there's that. They could have been wrong, sure. But absent further legal judgement, I'm willing to side with the decision reached by the team of lawyers over random Internet commenters.
> Microsoft's legal team obviously came to the conclusion that the emails and payment were at least sufficient to grant Mojang a license to the artist's work
Who knows. They might have thought that litigation costs would be small enough, or it might have slipped through the cracks. We don’t know what Carl told them.
Not necessarily. They might have concluded that the potential liability from non-ownership was insignificant compared to the upside. Even when courts find against corporations who have massively screwed artists the compensation tends to be modest, and this case isn't clear cut.
Beware that this is very dependent on jurisdiction. There are places where such informal agreements are completely non binding. IP laws vary quite a lot as well. So your intuition might be completely wrong. Just sorting this out would be a nightmare (the author was working in Germany for a Swedish company; which law should apply? Then there is Microsoft).
> If Microsoft replace the poem, I'm not sure anyone would notice except the author wouldn't have a fun fact for his bio.
He would still have it: this happened and whatever happens next won’t make it un-happen retroactively.