Would I still use the canonical tag for the child posts?

Selected answers from the Dumb SEO Questions Facebook & G+ community.

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  Thai Bui: Hey guys,
  I am building a site where users can edit each other's post.  ;I know that you can use the canonical tag to tell the crawler the preferred page. Would I still use the canonical tag for the child posts? The reason I ask is that even though the child post is the direct copy of the original one, it's slightly different because it has been edited therefore it's unique.
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  Shawn Cohen: If the child pages only exist for the users, it might be better to add noindex,follow tags to each of the child pages since using rel=canonical here seems to be bending best practices on its usage a bit.
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  Thai Bui: What if we wanted to show the post in searches though?
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  Shawn Cohen: If you want them to show in searches, then rel=canonical is going to negate that anyway. One way you could make them unique is to make it plainly obvious what has been changed from one version to another. if you wanted to display those one at a time, you might be able to paginate and then add rel=prev/next tags so that deeper pages could be indexed and then see what happens. Still seems like it would get flagged as dupe content though.
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  Thai Bui: Ah, you're right. Either way we're telling the crawlers not to index it. I'm wondering if allowing the crawler to index these child pages hurt the site. ;I'm definitely using rel=prev/next for paginated pages.
  
  Thank you so much for your input. This is something I have to figure out.
• 
  Shawn Cohen: Yeah, you're welcome. I've seen some sites like rei.com using prev/next and their deep pages still be cached. Not sure what sort of visibility they get but they are accessible to Googlebot and do get indexed.