What is `!-*f(6s6U8Q9b` here:

  const questionCriteria = {
    filter: '!-*f(6s6U8Q9b' // body_markdown and link
  }

I thought maybe it is a hard-coded CSS element name in StackOverflow answers, judging by the context, but it's not that. Could you shed some light on this?

Found in the How2 source file `how2/lib/how2.js`. Thanks.*