Well, Sierra definitely has January 1996 beat:
My guess would be that if you can track down copies of InterAction magazine from 1991 and 1992, that would be your best source. Perhaps the person running the above site will be able to send you scans of the relevent articles.
I don’t believe I ever played TSN/INN after my family moved to Seattle in 1993 (Netscape was released around then and I was busy surfing if I was online), so as of Spring 1993 I can tell you for certain that it had the following features:
There was a map with different “worlds” (essentially lobbies for arranging games) that you could select.
In the upper left was Larry Land, which is where you could play casino games (poker, hearts, slots, roulette, and perhaps more)
In the upper right was Yserbius, the role playing game.
In the middle-right was the “Other” section I believe, which had all of the various board games (checkers, chess, boogers, 4D tic-tac-toe, backgammon, etc.) and action games (paint ball, and Red Baron the 3D flight simulator)
^The above might be slightly off–perhaps there was a fourth land?
Larry land and the “Other” section when you entered would put you in the lobby. down the center of the screen was a list of tiles with the players names. A control panel ran down the right side of the screen. I don’t accurately recall the method for starting a game. I’m currently thinking that for some games there were rooms that you could enter if they weren’t full, and for others you would invite people and if they accepted then a game session would be created for you.
Yserbius was largely the same, except that they used a different lobby, that was supposed to be the tavern outside of the volcano, Yserbius. You would form a group and then enter Yserbius looking for goods.
Looking at the page you linked to:
“Real-time multi-player online games” – Yserbius was realtime or at least fairly close. There might have been some sort of semi-turn-based type thing in there just to make synchronization easier. But Red Baron (which was also part of TSN/INN) was full real-time amongst multiple players. Whether it was full blown MMO or not I don’t recall. I have a feeling like I recall being able to go out solo and be able to find and join other groups who were also already out adventuring–which would make it MMO, but you would need to ask more people who remember better than I.
“including card games” – Yes. Listed above.
“real-time updates to ladder rankings for multi-player online games” – I was #12 or #21 on teh Backgammon ladder. I am fairly certain that upon winning or losing a match, my ladder ranking was instantly updated.