Reddit was/is first come first serve (not exactly sure how it is now post-mod-strike). Whoever started a sub “owns” the sub. Any sub could choose to lick boots or talk shit for or against any company. The site admins would rarely if ever step in.
It’s essentially the same with lemmy but each instance’s admins will set their own rules for when to step in. It doesn’t really matter because a company could (and honestly probably should) start their own instance if they care to control messaging.
Likewise, anyone wishing to be critical of a company can always start their own instance and then they have the final say without worrying about how a particular instance admin might react.
This is one of the built in advantages of federation.