A rarity listing

I notice on some achievements I am the only person on the site who has that achievement. Which makes me wonder how many in total I have that way.

Would it be possible at all to sort achievements by rarity-by-number ( how many others have that achievement ) or rarity-by-percentile ( only 2% of people have this one )

There's a number of sort options. Sort by TSA ratio is probably the one you would want to use.