I just tried replying to a comment by typing "@Luís: " and submitting it. After submission, the user name as well as the @ symbol disappeared. I tried editing the comment twice, but the "@Luís" part kept disappearing. Even deleting the comment and reposting it did not help.
Since I already posted comments which referred to users without any special characters in their names, I'll have to ask: Is this a bug? If not, how can I refer to users on askubuntu who have special characters in their names?
Best regards Andreas