Will a committed person who set up a forum and chat rooms (text and voice) for his village and laid down instructions to fear God and only say or write what is good incur sin if violations occur in these rooms in the absence of a monitor?

The questioner is congratulated on his commitment. If some users of the forums he established make mistakes and do not adhere to what was requested of them, there is no sin upon him, because "no bearer of burdens will bear the burden of another," and it does not harm a person if others use for evil what was intended for good, as long as he did not intend evil.