CAS login is case-sensitive
I am able to create multiple .cards accounts by writing my CAS user name differently: user names "abcd12" and "Abcd12" -- even though linked to the same CAS login -- will result in two different .cards accounts.
This is problematic because on a mobile phone, the first character is always in upper case, whereas on a desktop PC, one will most likely type the user name in all-lowercase.
A first investigation about the root cause suggests an error in the CAS package used by .cards.