Quill Coat Passive

The reason is so that you don't kill blue or red when you're trying to donate it to your ally. Same reason Riot changed the % chance to deal 500 damage with Wriggles to a flat amount. Personally, I think it's great, it's like having a mini-respawn in your jungle. You gank, then you go kill all but one small wraith and sit there soaking health and mana regen before moving on to gank mid.

I was thinking that as well, but, however, red buff can kill monsters; so i don't see the actual reason the Quill Coat passive can't kill them.

It is good, and it does mention that it can't cause lethal damage I believe. I love that, otherwise I would take blue's I want to give, and I wouldn't have my mobile refueling stations without it!

this is so that you dont take things like blue buff by mistake- i was worried that the item would take blues from your mid lane at first and then used the item and glad it is true damage and not magic so that there is no exploits with spirit stone and that the passive cannot execute to ks buffs away from teammates