Yes please, to both of the "similar racks" suggestions - only count unique modules, and reduce (nearly) duplicate rack results from individual users.

Also, it would be nice if racks with different available space were down weighted. If I have a 3u skiff with 10 modules in it, I would prefer to see other similarly sized racks. I don't care about someone else's rack that has all my modules plus 90 others.

Maybe something like (number of similar unique modules)/(total rack space ratio [big:small]) would be a good metric.