How are coins distributed?
Just tried it now, with my opponent guessing my 3-coin word and me guessing his 2-coin word. After both were successfully guessed, I see that I only got 2 coins. Thus you only get coins for successfully guessing your opponent's word.
EDIT: Here, you can see that an employee answered a similar question incorrectly by saying that it is equally distributed. This is wrong because, along with my experiment above, then a "Coin Distribution" chart would not exist in the stats pane.