One thing that I do notice is that the recommendation engine appears to consider downloaded previews. So, if you download a preview, but don't like it, Kobo still appears to count it as something you are interested in.
I also feel it gives weight to any books you simply click on to find out what they're about. If I see a book that I think might be interesting by its title, only to find that it's a romance novel (or whatever), then I'm plagued by romance novels for months to come. It makes me fear even looking at books anymore.
Then there are the continual recommendations of books I have in my library. How simple it would be to correct that problem by looking in my library. Just exclude those books - I've already bought them.
And when I click on "Already read this book", then exclude it. Don't keep recommending it.
I'm not a programmer by trade, but I write lots of programs. I could fix their problem in a heartbeat.
Are they purposely trying to annoy everyone?