That’s not how it works. See the parent.

They said that they use it for metrics, so clearly there must be an "elon impression" metric.

I imagine it's the largest metric in a mission control style room

it starts dropping, klaxons start blaring, the room drops to red only lighting, engineers on the floor start pulling out their hair knowing the shitstorm that's coming

Yes, it’s not making anyone see any extra Elon tweets as your comment alleged.

It means they won't ship features that hurt Elon's reach. So in a sense, it is biasing code changes in favour of Elon.

Why does it mean that?

Thankfully they haven't added a "no mute Elon" feature. Yet.

They don't have to, because he effectively can't be muted. People tweet quote him with an image, and it's not blocked even though I have him blocked as an account. This behavior is pervasive enough that you can still see his tweets all the time.