what is a troll thread?

In Internet slang, a troll is someone who posts inflammatory, extraneous, or off-topic messages in an online community, such as an online discussion forum, chat room or blog, with the primary intent of provoking other users into an emotional response or of otherwise disrupting normal on-topic discussion.

And by don't feed them, it means don't reply.

Also stay away from softbanker, he seems to be the only one trolling users directly.

Avoid pointing any fingers my friend.