Difficulty categories are a mess to deal with for any game with them. I'm using Hard, Normal, and Easy as generics for reference.

• Separate categories for difficulties - Can cause a lot of clutter if there's more than one or two categories (like Any% and 100%). You need to check each one to see the times. On the off-chance a hard run is faster than an easier run, it might not be noticed because they're not stacked against each other. Especially so for Normal, since middle categories are often ignored; people look for the fastest and/or hardest runs. • Subcategories for difficulties - A little better, but still has the problem of different times being noticed. Defaulting to one kind of screws over the others. • Difficulties are recorded but are on the same leaderboard - This puts easy and hard on the same board. In most cases easy will be on top, and since hard runs are below easy, even for the best hard run, it'll skew the perception of it since it has a lower rank. • X difficulty only - This isn't very fair for players who do the easiest difficulty for speed, or for players who do the hardest for the challenge. • Hardest and easiest difficulty only - Probably the best for most games. Sometimes middle difficulties have enough difference to justify running it too, though.

I thought of a possible solution for the site to add. It doesn't address all the issues, but should get most.

Categories for up to certain difficulties - Example being Any Difficulty and Hardest Difficulty. This separates the two main concepts: fastest and hardest runs. Defaulting to one doesn't hurt too much since the category title shows which one users are looking for. For games with notable differences for middle categories, a category can be enabled for Normal+Hard.

There'd need to be a 'sequential' setting for variables for this to work, meaning the values higher on the list are considered greater than the ones below. Then subcategories are set for upto said values.

Edit: Now that I think about it, this could somehow extend to platforms and regions, too.