Let me first admit I didn't read through all the related topics. But from what I've read, I don't think this should lead to a permban.
As far as I know, the plagiarism bans got so strict only because of many users spamming the forum with other people's text to earn money (or more recently Merit). On any other forum I know, users don't get banned if they copy some text that can help someone else, and it's a pretty common thing to do since the beginning of the internet. But on any other forum I know, posts don't lead to direct earnings, so it's not a big problem there.
Of course the classic "everybody else does it too" is not an excuse, but I think it's worth to differentiate between illiterate spammers who use this forum as an ATM, and real users who slip somewhere.

Note: I don't know guigui371 at all, and I can't read French.