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I would refer you to Merriam Webster:
Thanks for referring.I would refer you to Merriam Webster:
Quote
to steal and pass off (the ideas or words of another) as one's own
Nothing in any of the posts cited in the OP are claiming to be anything other than the authors original words. No additional rules are necessary. But just quote half of definition.
The full definition is:
: to steal and pass off (the ideas or words of another) as one's own : use (another's production) without crediting the source
Btw, can I say you do plagiarism by "half" your definition? 
One more thing, tell me, how should I quote the words in http://p2pfoundation.ning.com/forum/topics/bitcoin-open-source?commentId=2003008%3AComment%3A52186, the first paragraph. Then post it on the forum