I know Discord has a system where each user has a unique ID that can never ever change, and is public to everyone. The client uses that ID to pull their current username, profile picture, etc, all of which can be changed because it is always associated with that unchanging ID. Surely Oculus/Meta has a similar system, right? What i'm wondering is how that system works, how a user themselves can see their ID, how games use it, and is it safe to share this ID like it is on Discord? And also if it is permanent, or if it can be changed (which i'm sure would be bad)
There would definitely be a unique id per user internal to Meta. But that's not public.
An application can request the user id (a 64 bit number), but this id number is unique to each application. So if Beat Saber thinks you are id 1234567, Pistol Whip might think you are 5217394. That means you can't use an id from one app to find a user in another app.
There are also organisation scoped ids. These are id numbers that are consistent between every app made by one developer. So for example Lone Echo and Lone Echo 2 could get a common ID for you.
The forum also has an id number for users, you can see it if you mouse over any user's name. I don't know how this matches the Meta ID for vr users (probably doesn't).
so if you, let's say, take oculus support's advice and factory reset your Quest 2, and redos load all your games, is the ID shared to each of the games the same as it was to each of them before? because i see lots of cases where people actually listen to the support staff and then lose all their progress, and i wonder why they can't just get it back
Cloud saves are optional for games, the developers had to manually add code for it, and many didn't, so factory resetting would lose progress.
Then at the end of 2021 they added a new system called cloud backup that they claimed would backup all local game data. You have to turn it on in the Quest settings menu under System / Backup. The message there says only supported apps are backed up, not all, so the initial claims were wrong.
You can see a list of which apps are backed up and when it last happened by going to https://secure.oculus.com/my/cloud-backup/
So factory resetting should in theory be safe for any game in that list that has a cloud save listed.
but i'm wondering if games could have their own internal databases associating the user's ID with, say, the cosmetics they own. so i'm wondering if that individual ID (that is different for each game /developer) gets reset when factory resetting, even if the user logs in with the same facebook account