I did not plagiarize, but I am the owner of the account in the other forum and it is natural that my writing here in this forum is similar to my response there in the other forum and I can prove in any way you want that account belongs to me.
It makes sense that both can be same in theme of the content but it's unlikely that it will be same words by words even though both persons are same. Can you prove that you own the cryptotalk account too by any way? If you can, may be you can get unbanned if mod consider the proof as valid although it's still plagiarism as long as you didn't add a source.