I always speak kindly of other people.

Ten seconds after somebody leaves the room, a small opening appears. Someone makes a face, or starts a sentence with "I mean, she's lovely, but." Everyone knows the shape of it.

Whether you step into that opening tells the others something they file away without discussing. If she gets it here, I get it when I leave.

Speaking well of an absent person is not a favour to them. They will never hear it. It is a message to the people still sitting there about how safe this table is.