I'm planning on running this game with some solo runs, but also doing some co-op runs with my cousin and some time 3 player co op. I'm wondering how co-op runs will be handled on the leaderboards. I tried looking at the D2 original leaderboards to see how it is handled there, but it confused me a bit to be honest.

I don't really think the original leaderboard had a place for this, but I would assume that maybe we could consider this for a category extension thing in the future? Since things are still fresh here and we're figuring things out that could be some weeks/months away though.

Totally forgot about co-op. It's a good thing you mentioned this. Would have been much more difficult to make the category adjustments later.

To make co-op and other categories possible on speedrun.com I had to change the layout a bit. I made the mistake of not thinking of other categories through initially and only had the usual solo Baal kill categories in mind. I fixed my mistake.

I currently added 8man, 3man and duo categories into co-op. When submitting runs into categories with less than 8 players then the speedrun.com intended method is to just leave those players empty and select a category with the correct player amount.

Our load time removal tool also works in mutliplayer. Does it make sense in any way to use it in co-op runs as well? How would final "time without loads" look like if there are multiple runners? Is this something other games have a solution for already or are co-op runs always real time?

I guess one solutions is to add together all the runners time without loads and calculate an average. If it's needed at all...

For me co-op is real time only, as the most competitve. My subjective opinion an average no loading time does not carry informational content.