How to stop freinds from seeing posts that i like or comment on

I have several people in my freind list that i have designated as an "acquaintance". When i post something to "freinds except acquaintance", those people cannot see my posts. I know because i coordinated with a real freind who verified this to be true. (I temporarily designated her as an "acquaintance" and she could not see my posts). HOWEVER... anything i commented on or liked (even if the person was not a mutual freind), it would show up in either her news feed or notifications! Very frustrating. How can i prevent this from happening without having to completely unfreind these "acquaintances"?