I find author notes fine as long as they’re not extremely long and not full of unnecessary random stuff like “I just got out of school, what are you up to for summer?” If the author note contains anything random, then yeah, I’m not a fan. Random stuff should be put in the forums (that’s what the Cafe is for). Important things that are relevant to you as an author, profile, or stories should go on the message board.
Author notes (on every or every other chapter) should be kept short, sweet, and to the point. If you have an announcement like a change in schedules, slower updates, a hiatus, or a revised section of the beginning is up (or something of that sort) is a good for an author note. The message board is fine, but there are readers who don’t check out profiles, so it’s good to spread the news. Otherwise, author notes should only be meant for specific questions (like “What did you think about this scene?”) to get readers engaged more and also a reminder to vote, comment, add the story to a reading list and so on since there are readers who forget to do these things.
Personally, I do two author notes that are put into separate chapters. The first author note (at the beginning) is my way to introduce the story. I tend to explain the main inspirations, what you can expect from the book, and more. I also use the chapter for extra things. For example, in my story In the Dark, the author note has an extended summary, a trailer, and photos of the covers put on books, a Kindle, and a phone.
The one I do at the end is my way to close the story. I explain what I had in mind for goals (word count, etc.), questions I have for readers, and other things I may add.