Think it’s one of those things that can mean multiple things because it’s never been fully defined.
Twitter is the source obv as every tweet with your @ in is listed for you and your @ tends to stay in it without someone taking it out.
So one use would be if you’ve been @'d in an embarrassing or harassing you’d request that.
On the end of posts which don’t have to be hot takes but rather could well be honest points by people of colour or women etc it’s more about saying they don’t care if you disagree and want you to remove their at if you’re going to have an argument in the comments underneath.
But supportive responses or constructive ones are welcome in my experience