That's right +Tom George
and thanks for all the RT love btw and good to talk to you again (been a bit). There is no effective "canonical" protection between sites. When I must dupe between sites I do three things:
* Write about half new content. This muddies the water sufficiently.
* Change the image support and image alt text.
* Quote OUT the dupe (use block quote command and a reference URL that is no follow if needed).
I never just change image alt alone as that isn't sufficient, but any combination of 1 and 3 work pretty good AND I never "have to dupe" so much that I can tip the math against me. For a bit I was using +Scoop.it
's embed and then thought better of it.
It is probably fine, but scares me suffiently I don't use it anymore since it moves content from Scoop.it directly into my WP blog AS IS. Could argue there is enough wrapper difference, but who wants to trust that these post-panda days.
Panda's pattern recognition is so good, so fast why risk it? Google can do a few things with dupe content. If they see a consistent pattern they will split the PageRank between the uses of the content.
This is where author tags can protect. Used to be if someone copied your content hook, line and sinker they could get credit for your content (if they had the higher PR) or cause your rank to get divided. Author tagging protects from that because Google can identify the publisher vs. the copy.
If Google sees a consistent pattern they can penalize the site as a whole (been there, done that and NEVER want to play that game again). +Mark Traphagen
is right, these days when in doubt write new, better content.
The last point I would make is when you do dupe content strip out social shares. I would strip social shares EXCEPT when writing enough new content that the new post is really NEW.
If I'm duping because it is unavoidable I might no follow the link, strip social shares and otherwise make sure I can't benefit from the dupe. "Not benefiting from the dupe" is what canonicalization is all about, but NO there is no canonical protection BETWEEN websites.