Service Desk Rejects Emails for Non-existent User in Public SD

In a public SD, emails are rejects if the email address doesn't belong to any users and the emails subject contains the key of an existent issue in that SD. The user is not created either.

In this public SD, if the user doesn't exist, it should be created. It is in fact created if the subject doesn't contain a issue key, but fails when it has an existent key.

The follow error appears in the processing logs:

Unable to get user.

For some reason, this error is respecting the system language (though others don't) and in Spanish, the error is:

No se puede obtener usuario.

Not test in other languages.

Steps to Reproduce

1. Create SD
2. Select options 'Everyone with an account can access my Customer Portal' and 'Anyone can sign up for a customer account on my Customer Portal' to have a public SD
   • This should allow automatic user creation when emails are received from address not used by existent users, as per this documentation
3. Enable email requests
4. Create issue, say ABC-1
5. From an email address not used by any user in JIRA, send an email to the SD where the emails subject contains ABC-1 and the email body is not empty

Expected Behavior

1. User is created using the email address, as per the documentation
2. If existent issue cannot be commented, new issue is create with the subject as summary

Actual Outcome

1. User is not created
2. No issues are commented or created
3. The error appears in the logs

Alternative Behavior

To have a more verbose information about what has failed in the Email Settings' Audit Log, this at least give a better context to the administrator and without going through all the trouble to find out what is the issue behind this.

Suggested error message:

Email found to be created as {{issue key}}, and user {{username}} has no permission to comment on {{issue key}}