As has already been brought up in previous posts, using seeds in challenge mode doesn't appear to actually have any impact on the levels generation outside of the first level. As such, other than the first level the Challenge% and Paradise% catagories are pretty much identical. Therefore I suggest that the two catagories should be merged together into one.
I would suggest making Paradise% the main catagory that stays, while the Challenge% catagory is removed due to the confusion with seeds that it causes. Alongside this however I think the runs of Toastie, Renusek and Scypher should be moved on to the Paradise% leaderboard as special cases, as it would be unfair to remove their runs outright. If that is possible anyway, I'm not entirely sure how being a mod on this website works :p
Let me know what you think of the idea though! I'd like to hear everyone's thoughts on this.