I'll describe a system I've used in the past:
It was a completely separate system from the production site. We could browse users and look at their info (username, contact info, location, billing info, demographics.) We could also click a button "login as user" and we'd be granted a temporary token and would essentially become that user.
This system was only accessible via a single IP address, and had strict security requirements. When a user would file a ticket, we could find them in this user management system and log in as them, if warranted, to see what they're seeing.
This would be nice for issues that seem user-specific.
There's more to this about logging in as the user in a staging environment so you can follow steps and relay them without affecting anything they can see, but I'll save those for a later discussion.