2 things

[eberkain]

The Great Wall has a tag that says Obsolete: Dynamite, but after researching that I can still only move 1 square per turn in the territory of an enemy that has built it.

 

[Thalassicus]

Units and buildings obsolete when the player who owns them researches the tech.

The graphical display issue on the policy window is a problem that's existed for a few months, it's a vanilla bug in the way the policy window displays links.