I remember that there was an instance of plagiarism even against someone like "Lauda", who i believe was never at a loss of words and would have been silly to use someone else's words.
There was, yeah. I think Lauda even said something like if someone were to go through all his/her posts, they could probably find cases where there are missing sources. I am not 100% sure about this, but I think that's how I remember it.
Then again, writing 2000 plus posts over 4 years while reading articles and gathering information from multiple sources, is it possible that a person's words may seem plagiarized. I think it is difficult to come to a conclusion without some real world exercise.
I thought and wrote about that yesterday.
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.
Imagine you like helping others with their issues regarding Bitcoin, wallets, security, etc. Now imagine there are 5, 10, 20, X number of other people doing the same. All of you have similar interests, you are all writing similar recommendations, use similar terminology, phrases, etc. Sooner or later, there will be 2 or3 posts that lookalike. But that's why admins take their time and probably consider many factors before applying the ban hammer.