Why can't we have an undo button again?

[TheGreatErenan]

tl;dr:

1. If you can undo honest accidents then you can also undo intentional but poor moves, and this latter fact is arguably a bad thing for a TBS game.

2. If you can undo moves that don't affect the FoW, then players will get in the habit of being able to undo such moves, and now their accidents are not just "I accidentally made a move I didn't mean to!" but also "I accidentally made a move that I thought I could undo but I really can't, and I was just trying to get an idea of where my units would be afterwards anyways!" And the response they receive will be not only "try harder not to make mistakes" but also "don't make moves unless you really intend to make them."