Can I use hero Boromir's (tactics) first ability even if he is ready just to raise my threat into valour range for cards like hour of wrath?

Arwen ally is the card that make us ask that question a long time ago. And the answer is: no.

alogos, could you please elaborate on how Ally Arwen is applicable to this situation? Obviously, exhausting her is paying the cost of the action, and if you can't pay the cost, the action can't occur, but here the cost is able to be paid. Maybe I'm missing something

Im sorry, I don't understand what that Arwen has to do with reading ready characters. Could you elaborate?

I think the point with ally Arwen is that you can't exhaust for no reason - which you would need to do in order to be able to ready again, because no, you cannot ready a character who is already ready.

The real question is, if you give Boromir Hands of a Healer, can you infinitely exhaust him to raise your threat?

Hands of a Healer exhausts when you use it.

Didn't check enough... not the same situation. Arwen => you cannot exhaust for nothing, Boromir => cannot ready if already readied ?

Still..... I'm pretty sure the answer is no, since you cannot exhaust cards that are already exhaust.

We did have an official response saying that you cannot play Flame of Anor without an exhausted Istari, which is identical in its format.

Flame of Anor: "Add Flame of Anor to the victory display and discard the top card of your deck to ready an Istari character..."

Borormir: Raise your threat by 1 to ready Boromir.

Format being: "Do COST to do EFFECT." If you can't use Flame of Anor while you don't have an exhausted Istari character, then you can't use Boromir's Action unless you have an exhausted Boromir.