Why not add a “rarest” section to records?

I think it would be pretty cool - it could be based on the Numista rarity index, and it would highlight whatever coin you have that’s highest on it.

Because the expressions rare, very rare etc. are only subjective criteria, numista has decided NOT to use those subjective qualifiers!

On top of that,  the numista rarity index is a kind of a hoax, so don't believe in it. In the real world it's worth “nothing”!

It's not a hoax at all but it has also not much to do with what laypeople would understand under rarity. Numista is about swapping so a low NRI says your coin is as common as dirt or very popular to users or not very common, very new or of no popularity for high values.

So not to much sense to filter sort for NRI.

Not to mention that both a 1909S-VDB penny and a UK 1933 penny have an NRI of 2.

Why not base the “rarity” category that is being suggested on the mintage. I know not all have mintage numbers so those would be excluded till if or when, those figures become available.

The concept of rarity is very subjective. The “1909S-VDB penny” mentioned above as an example of rare coin has a mintage of 484,000 (which is 2420 times more than the Numista 2022 silver token) and is much easier to acquire than many coins or tokens considered as common (you can buy at https://www.greatcollections.com/Coin/1413398/1909-S-Lincoln-Cent-VDB-PCGS-AU-58-BN for example, but good luck finding this rupee from Jaisalmer).

Depending on the context, rarity can refer to a high market demand/offer ratio, a low mintage, a low number of surviving examples, ease to acquire, etc. The Numista Rarity Index covers one aspect of rarity and it is clearly defined here.

Because of the ambiguity and the subjectivity of rarity, I prefer not to implement any rarity record. (The idea was already rejected in the past).

NRI is 

It shows the percentage of users who own each year or variety among all the users who own the coin.

see details at https://en.numista.com/forum/topic72983.html

A coin can be very common in country A and very rare in country B
The number of members can be very very different between these two countries A and B
This number of members being necessarily linked to the number of inhabitants
and the number of inhabitants...

d'où le NRI est fonction de…