It is not possible to add multiple equivalent usernames twice using the JS UsersMultiselectWidget, e.g. "Admin 1" and "Admin_1". Since T274568, this is also the case for the PHP widget.
However, in both modes, the widget treats equivalent IP addresses as separate entries:
This is problematic because:
- Anything that handles the widget's values needs to ensure that the IP addresses are unique
- If the widget has a limit set, it uses up extra entries for equivalent IPs
An example of where equivalents are (unintentionally) treated as two separate IP addresses downstream can be found in CheckUser: