We actually recently hit this very issue - a bad account migration resulted in everyone having flastname accounts - but that first initial and last name were based on legal names not common names - as a result a number of employees were upset at being forced to revert to birth names, especially those who had immigrated at a young age and adopted a new name.

I have a friend who was named at birth after their absentee parent and really dislikes ever being called by that name. It is important and polite to use names that people personally prefer within reason.