Thanks for the post. With the TestRail licensing you are not charged for inactive users, but you are charged for the total number of users that were set to active at any time within the span of a pay period. This means if you deactivate users in the middle of a pay period, you will not see any decrease in charge until the next billing cycle is complete.
Regarding the forgotten users, there is not a way to remove them completely as TestRail does require having some form of user identification for any entity (test cases, runs, results, projects, etc) created or edited by that user. As BGanger mentioned, in the user list you can hide them using the “Show” dropdown menu on the right side.
The actual strings that are generated when forgetting a user is the epoch time stamp (in milliseconds) for when the account was forgotten in the system, which is why they’re not the prettiest to look at.
I hope that helps! If you have any other questions about your billing or TestRail functionality please feel free to reply back here or reach out to us directly at email@example.com.