Anyhow, back to the topic. How about introducing three strikes rule? First strike - a warning, second strike - a temporary ban, third strike - a permanent ban.
Any changes that were to be made concerning plagiarized content and account banning would just bring about new discussions and complaints, such as:
Where was this rule when I was banned? I only had one plagiarized post, why did I not get a warning instead of a ban? Etc., etc.
If someone browses this forum, reads books about Bitcoin, and watches YouTube videos on that subject, that person has probably acquired all kinds of info and knowledge that he will remember. Naturally, it's hard to remember what you heard or read where. But when making a post or replying to someone on Bitcointalk, you can always say something like: "
I read", "
I remember seeing", "
Member X said in one of his posts", "
I can't remember the source, but...."
All that relieves you of the responsibility that you are trying to make it look like what was written are your words. You don't have to cite the source for everything if you don' know it, but make sure to mention that someone else said it. I haven't looked into what Mpamaegbu and Pokapoka124 are blamed for, so this is only a general recommendation.