I create a omniscient copyright detection bot and face it at everything you create 24 hours a day 7 days a week.
You go home and sing happy birthday to your kid. The bot gives you a non-monetary warning for using a copyrighted work without permission. No big deal, but it is on your permanent record.
It had been a stressful day so you take up your evening hobby of painting. You like nature scenes and trees and 30 minutes in you receive a violation, evidently Bob Ross has already done this and his surviving estate is now asking you to destroy the picture.
The next day you go to into your job at the corporate bureaucracy slinging lines of javascript. It's been a productive day so far and you have a few hundred new lines of code written and then the bots going off and HR and legal are ringing the phone within seconds. Turns out some comment you'd saw on Stack Overflow years ago was imprinted in your memory well enough you committed a copyright violation. Looks like you'll be losing your job.
They aren't, or they shouldn't be, but that's the point of the parent's comment.
Look at the videos flagged by youtube or copyright trolls, a lot of them are not actual copyright violations, but they are flagged anyway by the algorithm and removed or demonetized. And it takes a lot of work to fight those claims.
No, that doesn’t seem to be the point of the parent’s comment. That comment is treating those activities like copyright violations when they’re not. Why would the parent imagine an omniscient copyright bot that is probably wrong?
Me singing happy birthday at home or painting a picture for myself to relax is already demonetized. There doesn’t need to be an omniscient (and wrong) copyright bot to do that.
The first situation isn't copyright violation because some monied entity went out and litigated against Warner/Chappell music. That's the problem with copyright - until you've litigated, which is expensive, you just can't tell what's in and what's out of copyright. You wrote "almost certainly" because of that.
I was hedging against the too-clever HN commenter coming back and saying, “The robot knew you were going to sell the painting” or “You sang the game on the Jumbotron at Yankee Stadium.”
The third exists in a form right now. I've worked for a couple of companies that require all code to be run through a scanner intended to detect if that code has been lifted from open source codebases. You won't get fired if it has, but you will be required to remove it before it is accepted into the codebase.