Do you personally find that online communities increase the pressure to fall in line with the "community consensus" on how a given RPG is "supposed" to be run and played?

Any given tabletop RPG can be only so comprehensive. There will always be facets of the rules, and practices on how to actually run and play the game, that the books simply do not cover.

Almost invariably, online communities for any given tabletop RPG will gradually devise a loose "community consensus" on how the game is "supposed" to be run and played. Yes, there will always be disagreements on certain points, but the "community consensus" will nevertheless agree on several key topics, even though the books themselves never actually expound on said subjects. This is most visible in subreddits for individual RPGs, where popular opinions get updooted into the hundreds or thousands, while unpopular stances get downvoted and buried; but the phenomenon is also present in a subtler form in Discord servers and in smaller boards.

To me, it feels like the ideal of "There is no inherently right or wrong way to play a given system" goes right out the window when someone mentions that they are running and playing the game a certain way, only for other people to come along and say something like "Yeah, but that is not really how most people play the game" (i.e. "You are playing the game wrong"). What matters most, is, ultimately, whether or not the individual group prefers to run and play the game a certain way, but it sure does not feel like it when discussing a game online.

I would like to add that I personally find that there is a fine yet very important distinction between "what the book says" (or does not say) and "what the 'community consensus' thinks the book says."

Ofttimes, I see someone claiming that "You are doing it wrong; the book says so and so." When I press that person to give a citation, they frequently cannot do so.