How should direct-fire targeting work?

[Zarel]

do commander-assigned units adopt the sensor range of the commander?

Nope.

So while currently, 2.x is using A, I still think I remember 1.10 using D.

By the way, I've discovered that this is false - 1.10 also uses A. Makes you wonder why they gave any weapon a range longer than 16 tiles (Missile Fortress's 31-tile range seems especially useless now).