I’ve installed new WordPress. I renamed an existing user ivucica to an administrative name (let’s say goblin), then I created a new user ivucica. This was done low level, by typing in manual MySQL queries, manipulating the wp_users table.

Then I installed Buddypress. Buddypress thought goblin was named @ivucica, while ivucica got named @ivucica-2.

Looks like there is a column in wp_users named user_nicename which is used by Buddypress and where this is pulled from. It doesn’t match the user_login column.