I read various blogs where YA books are reviewed, often thoughtfully, sometimes with added snark (Reviewer X). Sometimes in the comments the author will chime in to thank them profusely for liking the book, or maybe defend themselves a bit, in a non-confrontational way. Is it acceptable for authors to do this? From what I've seen it curtails any further honest discussion of their book (especially if someone didn't like something).Acceptable? As with many aspects of the internet, what people can do, they will do.
You're right that conversations on blogs sometimes get more polite and less honest when it becomes clear that the author is a reader. There's not much to do about that.
But authors should strive for a detached relationship with the criticism and commentary their works will encounter. You knew when you wrote the book that most people wouldn't appreciate it as much as you do, right? Or in the same ways?
It's important to remember that this is one of the magics of creating art, and one of the heaving frustrations. Ideally, your work will mean something personal to your readers, and that necessarily means it will be something different from what it meant to you.
So try to let go. Be philosophical about it, and remember the author's prayer:
God, grant me the courage to offer myself to others, the wisdom to let my work be what others most need it to be, and the serenity to hope that it irritates the jackasses of the world at least as much as they irritate me.