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I was actually talking about adding descriptions from a source to posts that currently have none, definitely not editing something made or put there by someone else, or adding stuff onto it (unless it's entirely sensible, like adding the already quoted person's name, which is clarifying).
Not much harm in that, and it's much more tidy to have that kind of info in the description box instead of a post (again, only if nothing else is currently in there). Because that's literally what it is, a description.
People screwing with them afterwards is very rare too, I can thankfully say from lots of experience. By the way, posts can be downvoted beneath the treshold, so that would ultimately be the same except irreversible.