You can be found partly liable for someone's suicide if you've encouraged or groomed someone to commit suicide. Saying mean things to them does not constitute such an action.
We can all talk about how reprehensible kiwifarms is, that it encourages reprehensible behavior, that we would not want to spend time with many of the people there in our lives, that we would disown our children for participating there, etc. But we have to put a stop to this push to take every opportunity to increase the scope of retaliation. We can't change the scope of what violence is or who is responsible for a suicide just because we find their behavior reprehensible and want revenge, not if we want to live in a just society.