Acoustics
The acoustics in the mastering studio, well as far as I am concerned there should be little to none at all. You don't want to have any acoustics that are misleading at all in the mastering studio. This is why the room acoustics need to be tamed by treatments in sound traps, proper wall & floor coverings that can absorb the unwanted transmissions of a room.
In some studios such as sound stages for recording an entire orchestra, acoustics like natural reverb are welcome. However, in the mastering studio, too much acoustics that have all these sounds bouncing around off the walls untamed would make a mastering job quite difficult an even worse, adjustments would be inaccurate.
The mastering engineer must have a clean clear echo free environment in order to really listen closely to what is going on in the audio. One good example of an unfit mastering environment is, if you have ever walked into an empty house with nothing in it an you talk or walk, you can hear the acoustics of the room very well. There is nothing to absorb the sound.
On that note it is good reason to discuss the acoustics when it comes to mastering to get an understanding of how not taming them can get in the way of doing a good job.