Considering Malak's name of Alek Squinquargesimus, I think Revan might also have an embarssing last name and not want to inflict it upon his child. Then checking Wookiepedia, I found out that there are planets like Quelii that don't use surnames for people and use the name of the town they were born in with their given name. Revan might not even have a last name.
As to Bastillia, she was still a padawan and could leave the Order without problems. Another famous padawan around that time also left the Order and was not considered a Jedi by ANYONE: Zayne Carrick.