I'm well familiar with the argument Anarchists make, I'm just pointing out that it appears to be divorced from reality. I'm also not claiming that hierarchy simply appears. I even provided a link in a different comment explaining why hierarchies become necessary for any complex organization https://www.marxists.org/archive/marx/works/1872/10/authority.htm
My argument is basically that hierarchies appear because they are effective, and if the current system was somehow overthrown, and this flat society was created, then we'd see hierarchies start forming because like minded people would recognize their value. Once that process starts people who choose to organize in this fashion would have competitive advantage over those who do not. This is just a process of natural selection at work.