Valve moderate steam forums themselves, unless companies opt out. But that’s only a relatively recent thing.
No idea bout Larian in this regard, but it’s possible that the bg3 forums are "only" moderated by valve themselves and your misgivings about Larian would be misplaced, but I don’t know for certain.
Steam moderators only ever get to anything if you report something. Then they will go look and decide.
Discussion moderators are assigned by the owner of the steam-dev credentials for the game and can merge topics, close topics, create new categories and all the other things that steam moderators can in fact not do. Steam moderators have only 3 actions, ban, delete, ignore (Do nothing). Assigned moderators have a ton of other features available to them to order a discussion, they also do not get any reports funnily enough, the reporting feature and assigned moderation people are different systems.
And just to make it clear, steam discussions are HEAVILY moderated. Reports are always going to lead to the above mentioned 3 actions. But developers would do well to employ proper moderation on steam imo. The current situation on bg3 steam discussions is driving newcomers away, and that is not ok imo
