This initially sent me into a temporary panic (id something change that undid all my permission settings with our categories?!), but luckily I was able to quickly self-diagnose.
If you change the category type when you are editing a Community category, the permissions may change to the default for that type.
Note: Ideation categories have been replaced by the Ideas module;
this is a legacy Type that will likley be deprecated at some point
This might only apply to the News category, which calls out some default permissions for that category. Which makes sense as to why any custom permissions would be reset to the News defaults if you switch to that type.
Luckily, I hit cancel when I noticed this and then quickly identified what had caused it.
Sharing to spread the word and populate in case others are panicking about this in the future. :)