Academia - What to do with "is plagiarism plagiarism" questions?

Every single semester, I explicitly teach my students a slightly more elaborate version of

Plagiarism is passing someone else's work as your own

And every semester, there is at least one instance of plagiarism by a student who has an existing (wrong or incomplete) understanding of what plagiarism is, and doesn't recognize the difference between what I told them and what they had previously understood.

For example, I think in that specific question, the OP had previously heard something like "If your project is the same as one of your classmates' projects, it's going to be flagged as plagiarism". When someone who has heard this reads

Plagiarism is passing someone else's work as your own

they may think, "Well, I've heard it's plagiarism if I submit a classmate's work as my own, so that definition is basically the same as what I've heard". Then, given that (mis)understanding, they may still think it may not be plagiarism if they're not plagiarizing from a literal "classmate".

I don't think this misunderstanding is unique to the OP of that question - I've come across this before. I do think there is some value to explicitly addressing common misunderstandings of plagiarism in the Q&A format.

Let me say a few things about a more general issue. Most of the questions like this and other similar repeated questions come from newcomers with rep 1 or 101 and little experience elsewhere. Many don't know how the site operates nor what they can learn from tags until they get a bit more experience.

Likewise many newcomers don't know to distinguish this site from a "chatty" email list and so write some things that are superfluous. Comments in particular often become chatty.

I think we need to be a bit tolerant of all such novice "errors" and pass them to the help page or otherwise help them.

OTOH, self plagiarism is a special issue since, IMO, it isn't universally understood. Ten or so years ago few worried much about it, especially novice researchers, of whom we see a lot here. So, repeating the definitions, and the reasons behind them, seem to me to be a good thing.

But it would also be good to have a way to mark canonical questions and answers so that those who want to help can quickly find a way to redirect the OP to the answers they need before there is too much redundancy in the site.