I had a story republished today in which I put the canonical URL in the sidebar of the draft editor, only to have an editor called Marina replace it with a generic blog.com URL.
The story appeared at the original site the week before, and I only have permission to republish so long as the canonical benefit of the the repost goes to the original site.
This also happened to my previous post of last week at Hacker Noon.
A cynic would say that HN is looking to appear to be publishing original material while enticing re-posters with the promise of canonical provenance to the original article.
If this is going to be an ongoing practice, HN needs to remove that sidebar option and make it very clear to readers that their work will appear to search engines either as a duplicate or a plagiarism, or an unauthorized republication.