Nope. That should be between the company and whoever did the post, frankly.

I don’t see how Glassdoor would have any liability unless they were somehow presenting it as their own opinion.

They might want to take it down as part of overall community moderation if it violates their TOS of course, say if it includes cursing, or has racist remarks or whatever.

I’m pointing out libel has a definition, and posting what is clearly an opinion isn’t it. It has to be making statements which are presenting false facts as true.

That they’ll almost certainly find ways to take down ‘undesired’ messages that paying customers don’t like seems like something they do, which is shitty and undermines their nominal reason for existing, is… sad but seems to be what is going on. Nothing to do with libel.