SAM

An acronym for "Self Appointed Moderator"
Typically a long-term or frequent user (community member ) found in comment sections and platforms like Reddit or Imgur, who lurks with the intention of downvoting and posting vitriolic comments to vent and control unwelcome posts. Ironically, often with venomous crafted text or graphics that explain how much they "don't care" about the post the comment is directed towards. SAMS are often trolls who intend to create an echo chamber within the forum they frequent.

I posted a comment on the news story and was attacked by a SAM for expressing a different opinion.