Modifiers for campaign relevance

[David Johnston2]

Originally Posted by downer

Another thread just reminded me that there is, as far as I can tell, no easy way to grade advantages and disadvantages by relevance to a given campaign. The problem is basically this:
What (except GM fiat) is to keep a player from picking a disadvantage that is possible, but from a campaign standpoint mostly or completely irrelevant? Say, a character has Thalassophobia. Sure, the world has oceans, but the player knows that the campaign is set.

Bad example. The value of phobias is in fact determined by how common their object is. If you are deathly afraid of something that doesn't actually exist in the campaign, that's a quirk. Rare is 5 points. Common is 10. Very Common is 15