[DanSmooth]

"As you start to rate articles in a topic, we show the predicted number of stars for all articles you haven't rated"

I'm not sure the average user would be actually interested in this, it might even be bad to show them the "magic" at all because they might try to game it and muddle their own results. He has the newest stuff you determined he might like at the top and is good to go (the focus should be more on the articles itself than on the ratings, although you need the ratings). More experienced or technical-savvy users might be interested in it, so perhaps make it an option to display this information if wanted.

Here is an idea so that you still get your ratings: What I have recently seen on lichess.org is the occasional reminder to vote their training-games. You should do the same. E.g.: If a user hasn't rated anything in a while. Or perhaps display just a reminder every few visits to actually get the data your tool needs to be better.