Plagiarism is undoubtedly both very wrong, and a major problem within the forum, but I don't see the benefit of removing someone who only did damage (plagiarized) years ago, especially if they are now otherwise being a member who is contributing to the forum.
There's a flaw in this ideology.
Let me simplify the structure of my thoughts into four alternative timelines for a given plagiarist.
P:= plagiarizing user
S:= plagiarized post.
1) P posts S. No one catches onto P. P, over a long time, contributes much to the forum. S is discovered years later. P is let go scot-free.
2) P posts S. No one catches onto P. P is an average user and much time passes. S is discovered years later. P is permanently banned.
3) P posts S. No one catches onto P. P is trying to contribute to the forum: they add
some contribution. S is discovered weeks later. P is permanently banned.
4) P posts S. No one catches onto P. P is not trying to contribute to the forum. S is discovered weeks later. P is permanently banned.
The difference between 1 and 3 is the time between the discovery of S and the time it was posted. One user is pardoned because of their contributions. Another is not because they did not fulfill the baseline requirements of minimum contribution.
¯\_(ツ)_/¯
Retort: "They should have contributed right away!"
If both users 1 and 3 had the same localized post quality and contributory status, the situation would play our similarly. (after all, if you're copy-pasting, it's unlikely your post quality suddenly spikes)
I am not arguing for anyone who has plagiarized to get off scott free, I am saying they shouldn’t be banned forever.
There is a reason why most jurisdictions has
statute of limitations laws, and I think there should similarly be limits for forum punishments, especially permanent bans.
If the plagiarism is only a week or a month old, any subsequent contributions are not going to be relevant. If a year or two has gone by, and in that time, the person has not caused harm, he has shown himself to be someone who will not cause additional harm if he is allowed to continue participating. The person who plagiarized a month ago has not shown this.
Also the administration should have caught the person sooner for the one plagiarized two years ago. Someone could have a legitimate defense to what they did, but might have lost the evidence or forgotten the circumstances under which they made a few posts years ago. I think the number of people with legitimate defenses are few and far between, however *everyone* has the right to get to try to defend themselves.