@Anonymous wrote:
If you are an authorized user on someone else's account it may or may not have any effect or your credit profile at all. The way it's supposed to work is that if you have the same last name and address as the account holder, then you get the benefits/harm associated with that account. Otherwise, it isn't supposed to affect you at all (good or bad). It doesn't always work out that way, though.
My wife (same last name and address) is an authorized user on my credit card. My credit limit appears as available credit on her reports, and when a balance reports on the card it reports on her account as well as mine.
I am an authorized user on an employer's credit card (which he set up so I could make purchases for him if necessary). It shows up on one of my credit reports, but it doesn't have any effect on my available credit or my current balances at all.
The reason they do this is that it's right for a spouse to share in credit history, even if that spouse's name isn't on the accounts. But it wouldn't accurately reflect my credit-worthiness if I benefited (or was harmed) by my employer's credit history (or that of a friend or cousin or someone else).
That's not how it works or perhaps I'm misinterpreting your posts: the data that is reported to the bureau is the data reported to the bureau.
Where it may or may not count is due to the anti-abuse algorithm found in FICO 8 (and presumably something similar in FICO 9) which may discount AU's from scoring depending on unknown factors: name, address are the two reasonable conjectures as to what they're matching on, but they could be doing something entirely different as well for all we know.
Hard to say without testing, namely number of tradelines with balances: if you leave a balance only on the AU and you get whacked with the same penalty as for all $0, it's being excluded. If you don't, it's being included.
Perhaps my understanding isn't accurate, Revelate. Thanks for your insights.
This post on Doctor of Credit ( http://www.doctorofcredit.com/how-does-being-an-authorized-user-affect-your-credit/ ) does suggest that the credit agencies (especially Experian) do actively try to weed out non-spouse AUs. I don't know how accurate that post is, though. And I don't recall where I read about last name and address (so maybe I just dreamed that part 
).
@Anonymous wrote:Perhaps my understanding isn't accurate, Revelate. Thanks for your insights.
This post on Doctor of Credit ( http://www.doctorofcredit.com/how-does-being-an-authorized-user-affect-your-credit/ ) does suggest that the credit agencies (especially Experian) do actively try to weed out non-spouse AUs. I don't know how accurate that post is, though. And I don't recall where I read about last name and address (so maybe I just dreamed that part
While I respect that site, when the post obviously misses the whole LBGT community when historically those AU's have worked even on FICO 8, I'd suggest the rest is a bit suspect too.
Anyway the bureaus can do what they wish with the data, but deleting data is usually never done so I'm a bit skeptical of that... fact is more data = more information = more better lending decision... and any UW worth a damn can read the responsibility line when evaluating a credit report anyway.
ETA: ah it's worse than that; Dr. of Credit, not so much in this case; I have a paper copy of a recent EX report which they mailed to me after a dispute, gender isn't even on there so it'd be impossible to really evaluate on anyway.