If trolls don't get moderated away, then they'll inevitably take over the discussion, while driving away legitimate readers. You can see the result in the comme

If trolls don't get moderated away, then they'll inevitably take over the discussion, while driving away legitimate readers. You can see the result in the comment sections of certain media outlets or social media. Simply ignoring that isn't exactly a sensible option. Especially when they start harassing third parties. However, publishing IP and ISP data from commenters is also quite questionable. Some jurisdiction don't like that at all.