They can revert shards. They can not revert individual accounts.
But in their reverting a Shard, don't they "also" revert an individual account with all it has in the bank box, character's backpack, House, stables and all that ?
Which leads me necessarily to think, that somewhere in the Shards' Archives that they have and use to revert Shards to a previous save, they "also" have individual accounts comprehensive informations....
It would only be a matter of "extracting" that individual account's information from the Shard's Archive when necessary.... sure, it is work that needs be done, but players do pay their montly subscriptions, don't they ?
The one question to ask, really, is whether the Developers may or not have the ability to "see" a LOG of an individual's account's actions in game.... for example, can they see that account XYZ "sold", donated or gifted a given item/pet, whatever, that was in possession of the account rather then having it go "poof" for some bug ?
Because, one thing is being able to assess that a given item/pet whatever was in possession at 00:00 on day X of an account and gone at 00:01 on day Y of that same account, another thing is "seeing" how and why that item/pet whatever has been gone.... that is, if from a willing action from that account, or due to a bug....
I think that this might more be the problem here, rather then whether or not individual accounts have an archived database or not...
Unless the Developers can "see" a LOG of all in-game actions of a given account, it is hard to be able to tell whether a missing item/pet or whatever has happened due to a bug, or because it was the account user who disposed voluntarily of that item/pet whatever in possession of their game account....
Personally, I think that it should be a Golden Rule # 1 of Game Design that games should be coded to LOG in any and all characters/accounts in-game actions at any and all times that they are logged, and store them for later retrieval and evaluation whenever needed (this could also come handy to assess whether or not an account may have been using cheats...). Such a practise would save a whole lot of headaches and problems with paying customers in the long run, me thinks.....