"Well you've obviously got a better working grasp of names and dates than I do,"
Understatement of the week.
"but I think you're mistaking precision for accuracy."
Those are synonyms, making this a distinction without a difference. You either fail to grasp logic, or basic English. I'm not sure which. Regardless, neither of these words refer to your grasp of history, nor your ability to ground theory within it. I'm not "mistaking" anything for anything, as your concept is demonstrably devoid of both.
"This is what I mean when I say that copyright (in the modern, IP sense) ultimately accrued to the author. "
Stop lying. You meant no such thing and you know it. Indeed, you very clearly said the opposite. Specifically. "In addition, from the very beginning, copyright was an individual author right that accrued to people, not companies."
And again "copyright (in the modern, IP sense)" means the legal ability duplicate, distribute, and creative derivatives from. Those were activities that the guild system specifically BARRED authors from doing. To say their need to buy manuscripts means that, effectively, these privileges "accrue" to the author is not true. And about "buying licences"; there were no licences to buy. You just made that up.
Let's remember the whole point of your original argument; that copyright - as an individual right - has "always" been the authors, and that our legal tradition has recognized "since the very beginning of printing." As noted, this is completely counter to reality. And now you're saying this isn't really what you meant, but sort of is because of these imaginary "licences"? Aside from the guild's charters, there were no licences. Only physical ownership and control of the manuscripts themselves, which was exchanged for money on unfavorable terms from the only legal buyers in town. Yes, that was a crappy system. No, it didn't give authors their due. And it ended in 1709, which is about two and a half centuries after the advent of movable type. Moving on.
"There was not much time following Gutenberg when it was legal for printers to copy whatever the heck they wanted."
True, but that had everything to do with censorship by the Church, and not respect for the rights of authors. Indeed, those two interests have tended to be at sharp odds. See my point above about authors and rights and who could do what "at the very beginning".
"Recognition of authorship was a social norm that predated the printing press, and was very soon incorporated into the regulation of the new technology."
If a custom pertaining to simple credit is your example of early copyright (i.e. what prevailed for the first 260 years), then you simply have no idea what copyright even covers. Just...none.
Also, who are you to say "very soon" about anything? Haven't we already established that your grasp of actual history is a confused and distorted mess of near bottomless error? Given your hilariously awful track record, you have no business making assertions about specific timeframes without clear citations.
"To return to my (now demolished) broader point, try this thought experiment..."
I've got a better idea. Instead of acting like a person who is quite literally moronic, why don't you take a moment to realize that you have been completely and totally schooled. Everything, from your grasp of history, to your understanding of words, to the honesty of your arguments, to the clarity of your theoretical understanding has just been handed back to you in shit covered shreds, and now there is a smoking crater where your credibility used to be.
This is where the normal, decent, reasonably self-respecting human would think "Wow, I really put my foot in it. I actually have no idea about any of this stuff. The worst part is that I didn't even realize how clueless I was. And there I was, starting of my remarks to others with snide personal insults about who belongs "in the uninformed camp". Instead of continuing to behave like an idiot, I'm going to spend some time actually learning about all this, and then, perhaps, I can save myself some embarrassment, and maybe even answer my own questions."
Questions like "Why would a major paradigm change in the economics and distribution of a particular kind of technology upset the related body of law that developed over the course of three centuries under an entirely different paradigm?"
You'll be pleased to know that this is exactly what my original remark covered. Provided that you're clever enough to realize that you were under some very serious illusions when reading those remarks, and not understanding them at all as a result, try going back and reading them again, and see if you can figure out the answer to your own question.
If you can't, then study harder. You'll know that you've got a passable grasp of history, politics, economics, and publishing when the answer to your question about trends in the marginal costs of publication and the extent of authorial control appears to be the opposite of your present understanding, for reasons that should be self-evident.
Good luck.