Savage Attacker
Once per turn when you roll damage for a melee weapon attack, you can reroll the weapon's damage dice and use either total.
Vigilant Defender
Starting at 18th level, you respond to danger with extraordinary vigilance. In combat, you get a special reaction that you can take once on every creature's turn, except your turn. You can use this special reaction only to make an opportunity attack, and you can't use it on the same turn that you take your normal reaction.
Since Vigilant Defender says you get to take the special reaction "on every creature's turn" and Savage Attacker says "once per turn" does that mean you can activate Savage Attacker on every special opportunity attack? I would have assumed not, but then this post from RPGbot was super confusing:
Savage Attacker is a bad feat. But hear me out: Once you get Vigilant Defender, you’re going to make a lot of attacks on a lot of turns. Savage Attacker works once per turn, so you can use it on every Opportunity Attack in addition to using it once on your own turn. Combined with the reroll from Piercer, you’re going to consistently roll well on that d12 damage die.
So it say's Savage Attacker is a bad feat, but then it says you get to activate it on every opportunity attack... which sounds great. So which is it?!