"Send your mother to the boneyard". I agree that's not table talk at all. But it is funny.
The unfairness about my example is that the player trying to take all 26 points, many times, even most times, needs to hide the fact as long as possible. Few hands are that strong that the player has complete confidence in taking all the points.
So someone pointing out that the other player might be "going for them all" can be the cause of the of the other player getting burned by missing one or two points.

Per Gambler.com -
In the game of Hearts, it is generally unacceptable to talk about the location of the queen of spades or notifying other players of someone threatening to "shoot the moon".

Not sure what you think is unfair about it. If somebody said, lead a spade so I can take a heart with it, that would be table talk and unfair. One of my most lasting memories is of my father constantly telling me during dominoes games to "Send your mother to the boneyard". I didn't think that was unfair either.

I was playing a game of hearts recently. One player had about 18-19 points. Nobody else had a point. Then another player said this: "somebody take a heart, make sure he doesn't shoot da moon ".
I think this kind of comment is unfair. Anybody else have a comment about this? What do you think?