So, one of my closest friends on here George Sepich and I just ran a test…
He commented on a video on my channel: ‘Great info’
He had the ‘share on Google+’ box checked (note: for the comment only)
This video then appeared on Google+ as a publicly shared post with the comment at the top. He then commented on his thread on Google+ and plusses my name.
This comment shows up under the original one on YouTube. I reply on YouTube and it pulls in his name (as you may expect) and this comment appears on YouTube and Google+ i.e. a comment can lead to a share and that starts a new post on G+, replicating comments back on the thread.
Google+ and YouTube are now fully integration and we can share content without using the usual share methods. p.s. if you only share to ‘circles’, then this is a post just to them.