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 have different username and display name. You entered the user's 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.

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 have different username and display name. You entered the user's display name and after you clicked on the display name, the forum added the username in ignore feild.