That's an interesting point. It's not really a block, though. It's filtering. I'm sure it's possible to include something like "Hide all content started by this member," but it wouldn't be a quick coding thing. They'd have to code every single area of the site and every potential interaction into that feed filter option.
It would be a fairly extensive project, so I know it's something we can't do right away, but I can add it to the list of potential future developments.