Not to be rude, but from this and your more recent post I'm not sure you get why Steam's forums being like this is a problem.
It's not an abuse of power on Steam for a developer to do this. Because they're a mod for the forum for their game. Valve probably won't do anything about this behavior because they don't want to do any moderation of the Steam forums themselves. They just offload it on the devs, regardless of all the work that might cause for devs when bad actors get involved. There's no accountability because it's easier for Valve if they don't have to hold anyone accountable; they'd much rather it be "your forum that you run is hosted here" than "we create and manage a forum for people to post about your game".
I think this is quite off-topic, so let me just state the reasons why I disagree, and then let's just agree to disagree or take it to PMs. Sounds good?
1- Steam is under no obligation whatsoever to provide a curated or moderated forum. Indeed, they aren't obligated to provide any kind of forum at all (the argument that they probably be better off if they
didn't is a different one, and one I can agree with).
2- A mod having absolute power in a forum doesn't absolve them from abuses of such power. I mean, this very forum we're posting in was created as a response to one such abuse.
3- Deleting factual information because it doesn't fit your narrative is a flagrant abuse of power. Again, I think we can think of a very prominent example considering this forum's story.
4- Steam probably didn't have in mind this blatant doctoring and skewing of facts when they created their forums. I simply contacted support to find out.