When Killing a player (and or named mob) a named trident will continue to use the kill message "<player/nametag> was impaled by <AttackingPlayer>, instead of saying <player/nametag> was impaled by <AttackingPlayer> using <TridentName>.
This could be a bug, or something forgotten by the Mojang team, either way it would be nice to see this resolved in future updates.
Cannot reproduce. I get the death message "<entity> was impaled by <entity> with <item>" (
death.attack.trident.item).