"Ostracize" does not work well online. You don't get direct feedback on how many people read what. (Even the downvotes are evidence that someone did read the comment, and expended some of their energy to downvote it -- which supposedly is part of what the trolls want.)

There is no online equivalent of a group turning their backs on someone in ice-cold silence. Just "not answering" is not the same thing... that happens to many normal comments too.