From Test-Scratch-Wiki
On profiles, projects, and studios
If someone makes a comment that you find offensive, you can report the comment as inappropriate so the Scratch Team will review it. If you report a comment on one of your own projects, then it will be immediately deleted in addition to being reviewed by the Scratch Team. If the comments are on a lot of your projects, you can also choose to contact Scratch directly with the contact us button at the bottom of every page: http://scratch.mit.edu/contact-us. However, make sure to not use the report button on the mean user's profile, as this is strictly for reporting inappropriate or mean content on the user/user profile itself.
Try to ignore the comment and not to respond to it, as it would only attract more attention to the unfriendly comment. Responding may also cause spam and flame wars. You also should not post in the Scratch Forums about it; it does not help getting the comment removed faster and, again, only attracts more attention. Instead of posting a topic about it, report it to the Scratch Team.
In the forums
If you find a mean post in the forums, just click the "Report" link and give a small explanation why it is unfriendly. It will pass the post to the Scratch Team, so they can review it and take action. Try not to respond to it.
What should I do if I keep receiving mean comments?
When a problem can not be resolved by just reporting one comment, for example when a certain user keeps posting mean comments towards you, use the "Contact Us" link on the bottom of every page to contact the Scratch Team. They will look into what's happening, and try to resolve the matter with you personally.
Prior to Scratch 2.0, there was a feature called the Ignore List. Comments or projects belonging to users on the list could not be seen by the list's owner.
