I agree with Jillian Smith Smith. I wish all names were displayed as:
First (LNAB) Current surname, even for men. That way, changes in spelling, changes of surname, and marriage changes would all be displayed. And the (Smith) Smith women would appear with both surnames.
As for the default, I am not sure what M is referring to. I would say that the LNAB is the default because the WiliTree ID for each profile is based on whatever is posted in the LNAB field.