I think this is especially true for large companies. Whereas a tiny startup may be given some leeway because people interact constantly and have a more defined culture, larger companies' culture are generally amorphous blobs that are more easily an excuse for bias based on common background/age/class/gender/ethnicity.

Yeah, some of that behavior is constrained given the paper trail that is left when interviewers have to communicate through collaboration tools. People are on their best behavior if they know they might get caught.

Absolutely. At open source orgs, the internal communication channels are way worse than the public ones. People advocate for positions all the time which would negatively impact their careers if made public.

I'm not sure what you mean by "open source orgs" or why you felt you needed to create a throwaway account to leave the comment. But, in general, "internal communications channels" on open source projects are something of an anti-pattern. Certainly, private board member (or other person-to-person) communications can be necessary but what you're describing sounds like an unhealthy atmosphere in general if there's a lot of contentious backchannel comms.

By "open source orgs" I mean entities such as all the non-profits which host/support open source projects.

You're right about it being unhealthy, unfortunately. It might be for the best if it dies and is replaced by something else.