So Durkon knows it's Tarquin now...

[Felixc-91]

There's no reason to think Durkon either saw or heard Kilkil. Kilkil made that comment some distance down the hall from Durkon's place of concealment. By the time Durkon emerged and was able to see, the smoke was concealing Kilkil.

That's incorrect. Look at the streched panel in comic 858 , Kilkil and the general were no more than 20 feet from Durkon's possition durring that exchange, the conversation flows well enough that Kilkil's line was probably only a few seconds before T notices the trap. Meld into stone does not interfere with hearing. It is almost certain Durkon heard them.
Edit:
Ok, maybe Durkon did not see Kilkil due to the smoke, and could not reconize his voice; but once the smoke clears (and its disipating fast) Kilkil will be plainly visible since he's on the orders side of the sliding wall/door. If D doesn't know yet, he will very soon.