I migrated my users of a phpBB2 forum to WordPress after lots of hours and after all this enthusiasm, I realized that usernames in Greek are not supported. I surprised as it is also UTF8 !
For example, I have two users as: (username/password) Κωστας/111111
and κώστας/123123 . As you can see the two users are different as they have 2 different characters (κ/Κ and ω/ώ) and in UTF8 these are indeed 2 different characters.
The strange thing is that when I enter Κωστας his password 111111 is not working, but password 123123 is working and the other user κώστας is logged in !!!
Please could you help on this..?