I think the clearest way to state my personal preference on the matter is this. If a character has a catch that is identical to other catches from other members of his group (species, brotherhood, whatever), then knowing his catch does not require "personal knowledge", it requires knowledge of his group. Such a catch grants a minimum +1 refund for its secrecy.
If a character has a catch that is unique to her and her alone, regardless of what other catches for other characters in her group are (if indeed she can be said to belong to a group at all), then there is a good chance that her catch is +0 for secrecy. Now if she become so famous that her catch is known to every Joe, Dick, and Sally monster-hunter out there, you can reevaluate the value of that catch. But at least as an individual catch it has the potential to be worth +0, whereas group-wide catches do not.
I'm not planning on changing anyone's mind with this post, mind you. I just wanted to put as clear a cap on my point of view in this matter as I could think of while full of Xmas leftovers and wrapped in a comfy blanket.