The interaction with regular lands, Damping Sphere & Mana Reflection is pretty clear. Since Damping Sphere don't have anything to replace until you have applied Mana Reflection you have to apply them so that you get C.

But what about lands that by themselves produce 2+ mana? Urza's Mine for example.
Now Damping Sphere kicks in at the same time as Mana Reflection which should let you, as the controller of the land, to choose in what order they will affect the event.

Mana Reflection -> Damping Sphere = Doubling mana to 4, replacing it with C.
Damping Sphere -> Mana Reflection = Replacing with C, doubling to CC.

Am I correct in this and if so, is this intended or was it supposed to work as Trinisphere, always applying last?

Edited Jakob Lernhage (April 24, 2018 07:14:38 PM)

You are correct; that is how Mana Reflection and Damping Sphere interact.

As for “is this intended”, if R&D wanted it to work a different way, they had (and still have) the ability to change the rules to make it work differently. They have not chosen to do so, and as such I don't particularly expect them to any time soon, since I have no doubt the rules team was already well aware of the interaction.