You have successfully blocked the user from sending you message, even if you see a different username in "ignore" feild.
Some users in the forum have different username and display name. You entered the display name of the user and after you clicked on the display name, the forum added the username in ignore feild.
I think you should be able to add the display name of the user, if you type it manually.
Right.
This is confusing, though, so I changed it to insert the display name now. Forum-wide, the display name is always supposed to be the name shown, though the username can be used as an alias in certain places.