[scribu]

What would those internal issues be? Wanting to be appreciated by your peers?

The argument made by the author is that the graph implicitly transmits a message which I think most of us don't agree with: "Passionate developers work all the time."

So, you're right - it's not harmful because it causes people to crave external validation. It doesn't and therefore removing it will not make the craving go away.

Rather, it's harmful because it makes the people who do crave validation behave in ways that are counterproductive for everyone.