Do quotes of plagiarized content count?
Assume someone posted something stolen from the Internet and later deleted it or edited it with a link. Another user quoted that post before changes were made. Can it be used as evidence of plagiarism? It is true that quotes can be freely modified by the person quoting the post, but when combined with the archived unedited version, it gives even more evidence of plagiarism.
No. There is no "official" archive of the forum and in any case, if someone fucks up but fixes it later you can no longer claim that their intent was to plagiarize.
And the second question: Everything on the forum is archived, why the user remains unpunished in case of obvious plagiarism and further editing? I mean after it became known to the public. Does it change something?
No it doesn't. If it did no one would ever be banned for plagiarism, they simply connect to a notifier like TryNinja's telegram bot and check for quotes and mentions for accusation of plagiarism, then quickly add a source link before mods take action.
Don't post the findings publicly then. Report to mods.
from my perspective anyone that's caught for plagiarism and at the period of been caught the user began to edit and add source, let the user face the penalty of plagiarism, it's absolutely wrong and if an adequate measure is not taken it will create a means to plagarise and edit when caught and definitely it will become norms of the forum.
So what? They fixed it, it's no longer plagiarism.
But when someone edit their Post after getting caught then they may deserve ban for sure.
No. Just no.
The goal should be reducing shitpostery, not banning as many users as possible. Report plagiarism to moderators but stop sweating about users editing their posts. The 1% who care enough to do that might turn out to be valuable users or they'll get caught later.