I highlight text while I'm reading it on a regular basis, almost never to copy paste it or do anything else, it just helps me keep track of where I am in the article. I pretty much never want highlighting to have any action except highlighting. Even if it didn't, it's breaking consistent behavior because highlighting on page X suddenly has completely different behavior than on page Y.

There should at least be a cookie that can optionally disable the service that can be set when it opens up. Would be pretty easy to implement and it would at least allow an out for people who think the experience is awful.