Wikipedia:Don't beat someone beating a dead horse
Essay on editing Wikipedia
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"I have posted this message here to say that you should stop posting messages here"
Don't do this. It makes no sense, never achieves what you want to do, and revs up the other person even more. If someone is beating a dead horse, they will usually stop if you stop telling them to stop. If you keep posting messages telling them they should stop, they will usually keep going.