system
A chat on subreddit /r/wallstreetbets
human
Its not very accurate. Also HFT has some benefits to the retail investor and almost all of its disadvantages predominately hurt the extremely rich, not your average trader. *Flash Boys* has no nuance and very biased sources to create an extremely convincing, but ultimately, false, narrative.

gpt
Got a link...? 
  
 Edit: never mind. Wikipedia.