While using Exert Influence, I noticed that some creatures who are captured who have gem activation abilities appear not to work for you, but for your opponent.
One such example was when capturing “Honored Hierarch”, after he is renowned, I had watched the AI match a gem that was marked by HH and then gain the additional mana from the captured card! When I had attempted to match one, it did nothing.
I noticed a similar situation when I had captured Void Attendant, destroying the activated gem does not produce a Scion.
I am guessing this is similar situation for most other cards that are captured.
(Created ticket regarding this)