Don’t know if someone else has already said this in the notes but unless your bookmark is private the author can look and see what tags or additional notes you’ve put on the bookmark (I like to check them to see if anyone has :D). Also, yes, you can add your own tags to bookmarks and make different lists to organize them!
You can comment on fics anonymously (though I think you have to log out to do so as of now, really wish it was an option while signed in but still great it’s even an option at all!)
You can save new chapters on fics as a draft (without the 30 day limit if I remember). I do this a lot.
There is separate sections for both beginning and ending author’s notes (you can use both on the same chapter or one shot) and using the author’s note doesn’t include your rambling as part of the word count. Which is nice as it doesn’t artificially inflate the numbers.