Elwynn Boar's effect makes it very clear what it cares about: It's not its Deathrattle triggering, but you having minions of the name "Elwynn Boar" die this game. This means:
Silenced Elwynn Boars do count towards the Sword, as the minion's name is not removed as part of Silence. However, if 7 Elwynn Boar died this game and you kill a Silenced Elwynn Boar, it does not give the Sword because the Deathrattle is the part that gives you the sword.
Effects that give the Deathrattle to other minions, or trigger the Deathrattle without killing Boars, like Tamsin's Phylactery, Xyrella, the Devout, or Necrium Vialdo not contribute to the sword. However, if 7 Elwynn Boar already died this game, then this effect can give you the Sword.
Transforming an Elwynn Boar does not contribute to the sword, as it's no longer an Elwynn Boar.
Countering an Elwynn Boar with Blademaster Okani or Poofing it with The Amazing Reno's Battlecry does not contribute to the Sword as the Boar was removed from play without killing it.
Also, most Deathrattle synergy effects look for minions which naturally have Deathrattles. Whether or not the Deathrattle actually went off is irrelevant. It doesn't count minions given Deathrattles through card effects like Tamsin's Phylactery or Libram of Wisdom.
Elwynn Boar's effect makes it very clear what it cares about: It's not its Deathrattle triggering, but you having minions of the name "Elwynn Boar" die this game. This means:
Also, most Deathrattle synergy effects look for minions which naturally have Deathrattles. Whether or not the Deathrattle actually went off is irrelevant. It doesn't count minions given Deathrattles through card effects like Tamsin's Phylactery or Libram of Wisdom.