Logins are case sensitive in PBA and case insensitive in POA.
"Case-sensitive usernames" is set to "Disabled" in POA. In PBA-E it is not possible to disable case sensitivity.
For PBA-E versions older than 5.5.4: to avoid creation of users with the name that already exists in POA the following w/a can be used: in
PBA Home> System> Settings> Security > Login Settings Additional Login Mask Filter set:
Then it will not be able to create users with capital letter in name.
Problem is fixed starting from PBA-E 5.5.4 - since this version PBA-E performs case insensitive check while creating user.