This tool can be used to identify crosspost and plagiarism ... http://smallseotools.com/plagiarism-checker/
Plagiarism should never be upvoted. Crosspost (where the original author is simply re-posting their material from another site) are subjective on an individual basis, but overall I don't feel they offer Steem much benefit and they hurt the site with search engines. I feel the author would be doing us all a favor by simply linking to the original post on the other website or deleting the content from the other website and waiting a few days before re-posting to Steem.
Cross-promote, don’t cross-post. :)
Exactly, cross promote, I've just seen an excellent TED talk here https://steemit.com/life/@connorcranston/best-ted-talk-period-how-to-get-whatever-you-want-in-life and it is a promotion and I feel the better for having seen it.
It made me think of this post again, nothing wrong with promotion, lazy cross posting never gets my vote, mainly because it never gets my attention.
CG