Why not just use discard as the mill keyword? i.e. Mind Rot would read "target player discards two cards from his/her hand" while Tome Scour would read "target player discards the top five cards of his/her library"

Having one word mean two different things has caused problems in the past.

Hi Mark :) I think, milling could be keyworded "forget". For example, Tome Scour would read "Target player forgets five cards". Simple and flavourful? What do you think?

The reason for keywording something has to do with needing to save text space, but it’s not needed everywhere just in specific places. The problem with keywording milling is it doesn;t tend to be in the places we need to conserve the text space. Remember that every keyword added adds a burden to a new player learning the game so we have to be careful when and where we add things.

Can you ask a developer in the Pit if Tome Scour is in M14 as some sort of cruel joke or if they think mill is a real sideways strategy in drafting that set?

Tome Scour is in the set because a lot of players like Tome Scour.

I was asked this recently: "In MTG, can you "return" cards from your graveyard to your hand, which were never in your hand to begin with? Such as Archaeomancer returning something that you lost to a Tome Scour. Logically you shouldn't be able to, but i suspect that in this case mtg probably shirks logic and lets you do it anyway?". It never occured to me that the particular phrasing of Zombify and Archeomancer effects could confuse. Has Wizards considered rephrasing them?

You can “return” things that were never in your hand. And yes, that wording has come up as being confusing.