When you gain a card with a Watchtower in hand you have three choices, which are nicely spelled out in three buttons. I like this - it's much better than other implementations which made you click the Watchtower card to reveal it and then do the action you want.
However, if the Watchtower is reacting to cards gained simultaneously it's difficult to figure out which one you are being prompted for. You have to read the log and even then it's not clear:
You gain a Duchy
• may reveal Watchtower to trash it.
• may reveal Watchtower to topdeck it.
The choice there is referring to gaining the Duchy, not the Duchess.
Feature request: Can you add the card name to the text of the 3 buttons so it's clear which card you are making the choice for?
Bug report: When buying a Duchy with the Watchtower in hand, there is no way to tell it to put the Duchy on your discard pile UNLESS you are willing to give up the duchess. Clicking on "Done Reacting" applies to both the Duchy and the Duchess.
Game 2210 is where I tested this after observing it in another game.