Gene is right. Rules have been set, and have been since the beginning.
This may sound a little Paranoid, but:
The main reasons why there is to be no Silencer talk is because of Liability. Here in the US, "Silencers, Moderators, Suppressors" are for the most part Illegal unless the person that has one lives in a state that allows them. Most states DON'T. The ones that DO, require them to be registered with the Bureau of Alcohol, Tobacco & Firearms and a Tax to be paid. Manufacture of silencers is also illegal unless you go through the lengthy process of getting the ATF to sign off & pay the applicable "Manufacturing Tax" .
Now I understand that Information is not illegal, but if someone were to come on here & got the plan to build a silencer from someone who has posted theirs, gets caught using it and says "Hey, I made this from what I found over a GTA" the ATF would shut the site down no question about it.
There's also the matter of "U.S. Homeland Security" They DO monitor things like these forums for this sort of activity. No, they might not shut the site down, but based on the information they find... They have the ability AND the right to find out just WHO the person posting is and end up going to his/her house and arresting them for use or manufacture of "Impliments of Terror" or whatever they call it. They've already done it with phone calls and have also made statements that they're Monitoring the Web.
IMHO It's better to simply not take the risk.