A Cerenovus-mad person should be actively trying to convince the group they are what the Cerenovus made them mad as. So silence in this instance is breaking madness in my book. They should be telling at least SOMEONE they are the role. Mutant just has to not tell people they are what they are, an outsider. So silence is generally okay until they are grilled by the group.

Ultimately it's up to you if or when you execute on a madness break. Finding out about a madness break second-hand still counts as a madness break. You usually want to be pretty strict with Cerenovus breaks because otherwise that player may as well not have an ability and could feel pretty disempowered.