You are right. Our assumption for now was that clickthroughs are distributed like upvotes. But we don't have any data backing this up. That's why we need to do

You are right. Our assumption for now was that clickthroughs are distributed like upvotes. But we don't have any data backing this up. That's why we need to do real experiments. And this touches to your second point that even on the real HN site, we don't have this data and don't want to track our users more than we do already. We're not entirely sure about it yet, but we could use an approximation instead. For example how long a story was shown on different ranks. After all we got some very good feedback from HN and are incorporating it into our research. So thank you for it, this is valuable.