It would stand to reason that any magical ward (even one with a Hellfire bonus!) would fall under said category and that a Warden could destroy one without harming themselves (unless it was containing something nasty 
). Otherwise, the swords are completely useless.
There's bound to be a limit to the amount of power an enchanted Warden's sword has available to it. Whatever that limit is, it seems almost certain to be much less than the Hellfire-infused lines of fire that made up those two pentagrams. In which case, if Luccio had stabbed it with her sword, it probably would've gone the way of the Denarian who fell into them at the aquarium; that is, poof into instant metallic vapor. Luccio would've pulled back a much shorter sword.
Or maybe Cowl's superiors didn't take well to the fact that Dresden managed to outmaneouver him.
As a leader of the Black Council, if someone in your group is about to become a brand new god, do you nominate yourself for the role, or do you hand it off to one of your lackeys, and just pray they continue to follow orders after they've joined the Mount Olympus Mile-High Club?
Myself, I doubt very much that Cowl has any superiors in the hierarchy of The Circle/Black Council. He may be one among many top people, though, ranked equally with several others in the group.
He talks about HWWB having left a mark on him, after that junkie in Storm Front sees him on the policestation and mentions HWWB.
We know there's a mark; we don't know that it looks like HWWB. For one thing, Harry himself had no idea what the thing's name was when he met it, so how would Random Junkie Guy immediately know its name just from seeing an image of it? For that matter, how would he immediately be able to attach the term "wizard" to what he was seeing about Harry?
Thinking about it, I'm having doubts that Junkie Guy was getting all of his information from the Three-Eye drug. Unless it gave some additional, prophetic powers beyond just insight into the nature of what was seen. Or unless the guy had been taking so much of the drug that his mind was no longer tethered properly to his own time and body.
It was also implied that whatever mantle Ebenezar had in mind for Harry, claiming Deamonreach as santum kind of nixed the idea pretty thoroughly. I'm very curious to learn the full significance of that.
The quote from the book is:
Rashid says that warning him about the island would be pointless. He’s a good judge of people, but I’m not so sure he’s right this time. The boy’s got a solid head on his shoulders, generally. And of all the wizards I know, he’s among the three or four I’d be willing to see take up that particular mantle. I trust his judgment.
That sounds to me like something on the island
is the mantle Ebenezar is talking about. It's a job involving Demonreach, one that has the Merlin ready to shite kine, but which Eb thinks that Harry might be ready for. Or that's how it seems to me, anyway.
