No, it is not saying to do it. John is familiar with what an order would sound like coming from Flint. He knows what suggestion would sound like, what it is when Flint has made a determination and means to see a thing done.

This is observation. John might do with it what he will.

It had been John who'd said to put that knife through Bertalan's throat, and Flint had obliged him. In turn, John looks down at the corpse, the pooling blood. (Feels Flint's attention like the press of fingers at his neck.) Knows innately the shape of the thing he could draw on to weave the spell, feels the hum of it in his chest, and hates it in turn.

"Stand to the side, where he can't see you," John instructs. Not that John had been innocent in the matter, but John hadn't wielded the knife. That makes a difference to a dead man, most likely.

It is the same here as it is anywhere else: there is the stain of this thing within him, and it cannot be severed, so he must bend it to their benefit.

With borrowed blade, John slices a neat line across his palm. The air around them, shadows and metallic scent of blood, seems to draw taut and close in by degrees.