These are messages 8, 9, 15, and 19. You can see that it skips over calling 8 but does actually call the others, though the requrements can never be fullfilled. I don't really know how it works.

HELL YEAH

Shame they don't display the character, but both of SEES' Links also display that, so

Kind of forgot that you can use the Social Link editor to. Edit Social Links. This is what they look like in the menu.

Which is exactly what Hashino said in Dengeki Playstation Vol.357!
あと、最初女性キャラはすべてアルカナの「恋愛」だったんですよ。「恋愛1」「恋愛2」って感じで。でも、同じものを育てるくらいなら、ほかのアルカナを育てるだろうなと思いまして、まだ完成していなかったショップのコミュをカットして、ほかのアルカナに振り直したりとか、最後までこの部分についてはいじってましたね。

It has 3 letter long abbreviations of the Social Links, but the order is the same as the order of the menu. So PER is short for Persona users, SEI for seito-kai, Japanese for student council, etc. Then we can see:

There's a Persona 3 beta available, for the US from 25th May 2007. Since it's so late, there's not really any differences between this and the final version. Aside from the debug menus, that is. And it's the Social Link debug menu I'll focus on.

The files for Elizabeth's request menu(which is counted as a shop) use both 'elega' and 'elevatorgirl', so it's likely that エレガ(elega) is short for elevator girl and refers to Elizabeth.

and エレガ.

There are also bustups with 武器屋(weapon shop), 骨董屋(antique shop)

There are bustups with the Japanese text ネット02(net02) and ネット03(net03). Guess those are the other characters in Maya's Link.

These might not count, though, since they do get used in the Fool and Judgement Social Links and Pharos has an unused reversed bustup as well.

All of SEES, including Aigis(which got used in FES) and the guys, have bustups.

The bustups that correspond to HERO'S usual number are instead an early Junpei, without the blue outline seen on the rest.

The file that stores the text about the Social Links in the menu(DATA/CAMP/COMU/DATCOMUHELP.BMD) is really weird. It's not stored in order of Arcana like Reload's, and has a few unused bits. They are, in order, with their Arcana number:

So, in the original Persona 3, there's evidence that the shop owners and Koromaru were originally planned to have Social Links.
#Persona3