(I'm sure people will say this is not technically a "bug" and that this is intended behavior. However, I think a moment's reflection will confirm that this is not desired behavior! Also, I don't remember this in the past; perhaps it changed?)
When I sorted my Library by "Rating" Logos sorts by my rating if it exists, OR the community rating if it doesn't. (Note: the community rating is notoriously inaccurate, since everyone has their own system of rating). This means that I see all my 5-star books (mixed in with any community-rated 5-star books), followed by all the Logos books with a rating between 4 and 5, then some of my 4-star books (mixed in with community-rated 4-star books), then all the Logos books with a rating between 3 and 4, etc.
I would expect to see my 5-star books, 4-star books, etc., all the way down to 1-star books, and then all the 1000s of books that I haven't rated.
I had just downloaded a new install, and wanted to very quickly download all the books that I had rated highly. With the current logic, this is impossible, and I would have to end up manually selecting them (I ended up sorting by % Read instead, which means I had to download more books than I needed). In the future, it would be nice to be able to prioritize books by ranking (see my idea here).