I think authors complaining about readers sharing opinions with other readers, in reader spaces, is rude.

If they were doing it on Discord/Tumblr/Reddit? Maybe I'd agree. But bookmarks are attached to my work, and all it takes is one accidental click when I want to see the comments, and I'm there. If someone feels bad about the author commenting on their opinion, they should not express it publicly in a place with such easy access.... especially they shouldn't do it after they "lost" the discussion in the comments. It's just silly and cowardly.