Forums sliding is real; its happened to me long ago when running a game mod. Id put a lot of work into the content, and most of it was stolen. The thief then created several fake accounts and had off topic conversations with himself in a bunch of other threads in order to move my topic onto the second page. At the end of the sliding, he'd comment on his own topic to put it at the top of page 1 and did this for months to keep it that way. Forum mods wouldnt be bothered to do anything about it either. They were afraid of backlash to ban the guy and somehow plausible deniability existed that over the course of months, countless times, every time I came up with a new piece of content he just happened to do the exact same thing a day or two later.

This technique doesnt work as well with todays social media; yeah we still use forums but they have changed and often feature many many many more threads on the first page than they used to - ala Reddit.