Fall flat the joke does. The Drifter does not grimace, does not wince, but a single dark blink of their eyes is the sole indication of their relative uncertainty in how best to respond to that.

In the end, they elect not to.

it perished
the Immortal Cell is no more.

So...yes. They were helpful. The Drifter cannot know with unflagging certainty that they succeeded, that the world is no longer the receptacle for another being's poison, a perfect cell corrupted and corrupting - but the finality of the last image in their mind's eye can allow for the hope.

They do not deal in hope. They deal in acts, in visualizing a foreseeable course of action and taking it.

But the shimmering glow of water, clean and pure, had been...

It had been the closest, they think, that a god gets to a promise.