I agree that you don't want deny messages sent out. It causes unecessary traffic on the network. For every packet that is denied, more packets are sent back. That just increases bandwidth usage. Same thing for email servers blocking spam. Never send back a message. You can cause your own DOS.
Another reason to not let people know it's denied is that if someone gets a deny message, then they have another clue as to what they need to do to try and get around it. If they don't get a deny message, then they are still left guessing as to where the problem is. I never provide any hints about security configurations to people who are trying to get through.
I'm not familiar with the Netgear commands; but on the Cisco routers, I always have them configured to not send out 'administratively-prohibited" icmp messages. I want blocked packets to just disappear without notification to others.
BierHunter
CNE, MCSE, CCNP