A mix of sodium acetate, oxygen, and chlorine gas results. The first two items aren't an issue, but the third... Let's just advise against mixing anything with bleach unless you have a pressing need to recreate WWI chemical warfare in your bathroom

It's a good thing. Bleach by itself is an inefficient disinfectant. You need a lot, which is wasteful. Adding a bit of vinegar to change the pH will make the chlorine much more available for disinfecting.

I used to keep a bottle pre-mixed. It won't last very long though, so mixing before use is better.