From the newsfeed, you can access all the content published on your accounts by users (publications, comments, private messages, etc.).
You can hide a comment on Facebook. Then the comment is not publicly visible except for the user who created it. You can also remove a comment from Facebook publication. From a comment in the newsfeed, select the icons “Hide” or “Delete”.
Contrarily, Twitter does not allow you to block a Tweet or a mention. We then recommend to reply to the tweet if you think it’s required.
However Nuke Suite does allows you to answer the user – see responding directly to users