Roles can help to keep conversations civil when the participants are benign as well as malign by removing communication friction. For malign actors they make it easier to pick out specific behaviours to review in one on ones and - if they persist - dismiss them for.
I know. My point is that large corporations have little in common with startups. A startup should not already be so ossified that it's possible for bad actors to get in and stay in.
In other words, if you get to the point that you need to wage legalese wars with corporate policy documents, you're probably not a startup anymore. We really need to stop treating big, 5+ year old companies like Twitter as "startups".