backseater; unwanted advice giver
Derogatory internet slang for someone who posts unsolicited instructions or criticism in the comments of online videos or live streams, especially Let's Play content.
Backseaters popping up in the stream's comments are annoying.
That backseater always gives detailed instructions to the player.
Compound of 指示 (instruction) and the derogatory internet slang suffix 厨 (derived from 厨房, 'kitchen', used for annoying or immature people).