Conditional formatting is at the layout level, so it gets filtered by your eyes.
Fields holding values, negative or not, are not sorted, it's the whole portal that gets sorted based upon criteria you decide.
Post some pics of what you are trying to make happen.
I'm not sure what you want.
Filtering may be able to set same condition as formatting.
If you want to sort only negative values as -1, -2, -3... it is "descending order"