[nomadrat]

I used to work for a big ad-tech company(the company is sold and closed now). I was a guy who developed a tool with this functionality. As a publisher, you can add a text with a link(plus tracking code) to every copied peace of text from your webpage. Something like: "Read more at: https://example.com/my-article/#<tracking_code>"

It's not about copyright. As a website owner, you can disable this behavior, but by default, it was enabled. The main purpose of this functionality was to track shares(for example if you copy text and send it to your friend in skype). As i remember it was one of the most popular & important features in the whole toolkit.

In a nutshell, it's about 200 lines of battle-tested javascript-code that worked perfectly fine in almost any browser(dunno about now it was around 3 years ago).

Personally, i hate this behavior.