There is an "Also share on Google+" option when you publish a comment under a YouTube video and proposals to make sure to untick the "Also share on Google+" option, which is currently on by default if you don't want your comment to be shared to Google+.
I was sure that not sharing just means that the comment will not be tracked in my Google+ journal but it will be visible in YouTube. However, I have noticed now that my comments are ghosted. They are not visible outside my account. I see the same "Also share on Google+" option when I make a comment in the YouTube blog.
"You control whether your comment will appear only here or also on
Google+. Either way, it's visible only to the circles and people you
choose"
pops up when I make a comment there. So, it seems that both Google applications ghost your comments, only YouTube does not advertise this fact.
Who can see my comments on YouTube if I do not G+ share them?
Can I retrieve the list of all my privately posted comments (I posted with option unticked)?
Update
Wait, I cannot even see the "Also share on Google+"-shared on YouTube. I can see them only in my Google+.
How do people publish the comments at all?
It seems that they are only visible if I reply to somebody. I see that this is discussed in YouTube Help Forum yet the majority remains unaware of that because, once you see your comment published, you relax. Nevertheless, you still can answer which difference "Also share on Google+" is supposed to make.
Best Answer
At this time there is no method in which you can search for your comments that you have made. The following is what was able to be used in the past but no longer works.
This use to pull up all results showing your comments on videos. Once you were able to get to the video you commented on you would be able to edit the comment or remove it.
As far as who sees the comments depending on if you selected "share on google plus". If you selected this it would post the comments to your circles for friends, etc, to see. If you deselected this option there would be no post made to google plus sharing the comment you had made. As the conversation that you posted about on the product reviews said "Product Reviews"... There can be a lag of about 4 minutes before a video comment will post.
I have also never seen a "ghosting" of my comment on my google plus profile or news feed. If I deselect the "share on google plus", it never gets shared and no one will see it. This topic at google is about 2 years old so updates may have been made by now to correct it.
I have done comments, shared and not. The ones I choose to share show in my circles and profile, the other I do not share do not appear anywhere.