This suggestion is to allow someone, who has captured another nation's capital, to be able to see the information from maps that were shared with that country for the next 2 days.
For example, if I share maps with Bulgaria, and the Ottoman Empire captures the Bulgarian capital, the Ottoman Empire would be able to see what my map looked like at the time they captured the Bulgarian capital.
Another example... If 4 nations have shared their maps with me, and my capital is taken by another player, that player will be able to see what those 4 nations' maps were like at the time he/she took my capital.
For example, if I share maps with Bulgaria, and the Ottoman Empire captures the Bulgarian capital, the Ottoman Empire would be able to see what my map looked like at the time they captured the Bulgarian capital.
Another example... If 4 nations have shared their maps with me, and my capital is taken by another player, that player will be able to see what those 4 nations' maps were like at the time he/she took my capital.