As the title says: Mark the Gold features we get to keep when we stop paying for Gold and drop to Silver.
I.e. put a footnote saying "you get to keep this feature even if you stop paying for the game" into the features matrix and mark the features accordingly (inventory and bank slots, BOFF slots, but not EC limit and character slots).
Or put it in the FAQ.
Easy to do, might reduce some confusion, people don't have to dig through the forums to find this information, plus it would be nice to have it officially confirmed.