Re: how does user data get added to the user page (not the profile)?
Once a user (student) has registered, you cannot change their username. Well, not without some fancy behind the scenes stuff. You can, however, have them change their display name. In the default BuddyPress install, this is automatically set to required when a user registers. It does seem like all 48 of your students do have their real, full names entered in that field.
So, it is just these 4 students. My guess is that they used their real, full names when registering their username. So, as an example, “John Smith”, instead of “johnsmith” or “smitty2cool”. If you look in MySQL’s backend and see this for the usernames of these four students (using my example):
John%20Smith
Then this is what happened. They used their real name, space and all. Now, the existance of the space in usernames can cause issues in WPMU. But, that is a different topic.
when I look at comments made by the students, I get only their usernames
Do you mean comments to blog posts displayed in BuddyPress themes, or comments seen outside of the BuddyPress environment?