This has been discussed many times in this thread. And this can not be considered plagiarism.
Why do you think this can not be considered plagiarism ?
It was an exact copy/paste of the post of another user.
You didn't forget to quote it properly, you didn't express any opinion. You simply just copy/pasted it.
If you just wanted to help someone / answer questions, why not either just quote it or use your own words ?
I don't think this falls under the category of mistakes mentioned by theymos.
IMO this is very clearly plagiarism.. anyway.. i wish you good luck getting your account back.
I believe that is the mistake theymos was talking about:
I know of one case where someone was banned for plagiarism in the recent massacre, but a very careful reading of the context showed that the person actually did just forget to quote, and by "quoting" the post they were expressing an actual point even if it constituted their entire post. This person was unbanned without any sigban, since this isn't plagiarism.