I question your premises, which treat quite disparate things as interchangeable and ignore temporality, and don't really address the previous points at all.

It's equally possible that people might want a channel for anonymous complaints because they don't feel comfortable or safe articulating their unhappiness over an issue in public - that is, they feel their own speech to be chilled, directly or indirectly.

Your argument seems to rely on the assumption that that can't be the case, based on events that have happened subsequently - as if the news from today about Paypal is necessarily a consequence of the Cambridge (not Stanford) litigation, when it might be in response to something else entirely; the substack author didn't bother to mention any recent controversies, perhaps assuming that her audience were already following the group's fortunes closely.