Trolls

A troll is someone who posts disruptive or unkind comments in order to elicit an emotional reaction from their victims. Trolling breaks the Scratch Community Guidelines. Because trolls are motivated by attention, the rule about dealing with trolls is to "report and ignore". This way, they don't get attention, but the Scratch Team can still ban them.

Sockpuppets
Sockpuppets are trolls use multiple false identities.