Difficulty flagging members using @

I've been having trouble flagging a post to members by using the @ sign followed directly with the members name. It has occurred twice when I was posting birthday greetings to members whose user name begins with a capital letter. Although I'd type in the capital letter when I posted it, the capital letter was changed to the lower case and the @ symbol was visible. Usually when flagging a member after posting, the @ symbol isn't seen and the member's name would show up in red. I attempted to edit several times making sure that I had the correct spelling of the member's name but after posting it always was changed to the lower case. I haven't attempted to flag someone with a user name that begins with a lower case letter but I'll do so now as a test using CCS moderator's user name. Can you help me out with this problem pianistclare ?
P.S. Okay so that worked as expected.