VM: 1. Most guys won’t take such a sign literally. Although they could have written it more politely, most guys wouldn’t take it seriously enough. (I know, I’m generalizing.)
2. It’s not a matter of not offending one guy and having some whispering, in Shuls where talking is ignored it eventually escalates to not a fish market but a chicken market. I’ve been to shuls where when there is a simcha the women’s gallery literally sounds like one -even during leining.
Emphasizing no talking is a necessity for a shul to remain a place of davening.