As mentioned NordVPN did pass with flying colours as it did what it said on the tin.
As alluded to above, this doesn't really
prove anything about your VPN. You still have to trust the auditor, and you have to trust that the VPN hasn't changed anything since the audit. Even in cases where a VPN provider has been subpoenaed (or another jurisdiction's equivalent) and has been found to have no logs, it only proves that they didn't keen logs
then. A case which was discussed on the forum a few weeks ago is that of Private Internet Access. PIA have previously been taken to court (twice, if memory serves) and had no logs they could provide. Many users might see that a ringing endorsement of their service. However, PIA have since been
bought over by a parent company (Kape) which are infamous for infecting their own customers with malware, and own another VPN with a very loose policy on sharing your personal data. Much like with bitcoin, past performance is no guarantee of future results.
Just for the record I do not use NordVPN, PureVPN, SharkVPN or any other I mentioned a couple of posts back, they were just examples since the OP gave an example and analogy of VPNs

As for what you say about audits and auditors along with a no logs/record policy - yes it is true it does not
prove anything because of the possibilities of altering the situation after the event. That same sentiment was also echoed excellently above by AdolfinWolf too and both of you are correct to highlight that auditing though might have some benefits it ultimately cannot be the seal of approval.
What would you say is the best way forward for mixers to try to get users to have full confidence when using their service?
(And a belated congratulations on becoming a Legendary member on the same day I made Hero rank)