When the topic is shown in html mode the @-character can not be entered in form-fields. Seems it get "eaten" by the keyboard-handler somehow. Maybe something like to Z was in earlier versions.
Are you entering @ by using Right alt button + other button? I think problems lies somewhere there. I cannot enter @ myself, too.
Will check it out...
I use the right ALT key (labeld "Alt Gr") and "2" on my swiss german keyboard.
I have no current sourcecode of feedreader here to look in. Maybe you have a keyboard-handler (like OnKeydown) that only ask the 2-key and set the Key-Parameter to "0" without checking the ShiftState (Alt). Just as an idea. Or one of the components is "eating" the keystroke.