I think Jon's post was a troll post, with some personal opinions (which are totally valid), a few technical criticisms (totally valid), but mostly "user error" and "nothing new."
The internet makes it easy to unintentionally plagiarize, the internet makes it easy to intentionally plagiarize. Jon makes the valid point that linking is better on the internet than quoting with attribution. He makes the invalid point that plagiarism of any form is Google+'s fault.
Specific ranking is a matter of opinion. Really what Google (the search engine) has to go off of is people's behaviors. If people legitimately like Google+ posts more than anything else on the internet, how would you have them behave?
Google (the company) is forcing you to use your Google+ profile to identify yourself to people who use Google Search, and Google News. Facebook is forcing you to use your Facebook profile to identify yourself when you post on Facebook. Yahoo! is forcing you to use your Yahoo! ID to use Yahoo mail.
Summary) Google+ is as valuable to you as you choose to make it.
Jon's post was designed to attract attention, not to lead to positive discussion. I responded in kind.