Sounds like a good policy. No one should waste their precious time responding to those who don't require or deserve a response. Here are a couple of quotations I dug up:
“Most of the successful people I’ve known are the ones who do more listening than talking.”
― Bernard M. Baruch
“We have two ears and one mouth, so we should listen more than we say.”
― Zeno of Citium, as quoted by Diogenes Laërtius
Second quote is not quite right for message boards, but I think you get the general idea.