TL;DR;
How can I automatically get rid of payer account that, due to specific conditions, do not have any identity linked anymore (thus being virtually unusable and just sitting there forever)?
Are those account even a problem from analytics/server point of view?
Background
Whenever a player downloads and runs the game we use the DeviceID (D1) to retrieve or create a PlayFab account (PF1) and link the DeviceId to it.
Then, within the gameplay, we let the player link additional identities (Facebook, Google/Apple depending on the platform). We do not offer PlayFab account linking.
We store the preferred login method and fallback on DeviceId if none has been linked yet.
NOTE: we do want to immediately and automatically create a PlayFab account linked to the DeviceId, so that's mandatory.
Scenario
Let's say that the player links Facebook account (FB1) to PF1. Now PF1 has two identities linked: D1 and FB1.
The player then somehow relaunches the game with a different DeviceId (new phone, uninstalls/reinstall the app etc...).
A new PlayFab player account is created (PF2), linked to the new DeviceId (D2). The game starts from the very beginning, this being a completely new user.
The player, having already linked Facebook (FB1) to another account (PF1) already logs in with FB1. We retrieve the PlayFab account (PF1) linked to that Facebook identity, and link the current DeviceId to PF1.
Now PF1 has three identities linked: D1, D2 and FB1
Problem/Question
This re-linking operation leaves PF1 without any identity linked, and that account is never going to be used again.
We would like to completely delete those "orphan" accounts without identities, as we feel it's pointless to have them around and they might just mess up our analytics and whatnot.
How do we do this automatically?
Is this even a problem? How do you guys suggest to deal with this issue?