If you create a new user with a username which has caps in it (e.g UCTstudent1) you can encounter several problems:
Realm Admin: adding the user to a realm with the capitalisation as above, the realm manager will show the user as belonging to the realm but the user won't have access if they login with the capitalized username.
Membership: if the user logs in to the site with the capatalized username, they can join joinable sites. However when they try to enter the site they will get a 'site unavailable' error. If the user logs in with the username in lower case they can access and join sites as expected.