Reddit is a pretty extreme example, though, where mods are basically subreddit dictators. For whatever reason, Reddit gave enormous amount of censorship and conversation-shaping power to mods, to the point where a handful of like-minded mods can enforce in great detail what is allowed to be discussed and what isn't.

Pretty sure if you unmasked the subreddit mods, the reason for the "circling around a particular brand recommendation" observation would become clear.