"Plagiarism" is not equel to "could not publish news from outside". We talk about plagiarism when you do not just "publish", but "publish" something that was created by other people - and don't even muse upon providing the references.
Paraphrasing:
 - you CAN "publish" the "news from outside sources" on bitcointalk.org, but;
 - you CAN'T "publish" the "news from outside sources" and forget to mention these "sources".
Because you can't take someone's thoughts and post here as your own (and of course you can't post the "news" here just to post something here, but that's a different story).
And all of these are not some unnatural, unusual, unprecedented or requiring-special-explanation statements - these are ordinary rules for every decent community, so I doubt that you actually "didn't know".

However, I hope that now, when you were banned, the rules (here is the Russian translation) will be the first thing you'll search for anywhere you go.