In three-pane layout, if you resize the list of articles column to be so narrow that "Actions..." does not fit on the same line as "Select: All, Unread, Invert, None" any more, then the Actions menu will cease to work. (The Actions drop-down appears on mouse-over, but it is not possible to access it because there is a gap between its title and its content.)
Perhaps it is possible to enforce a minimum width for the list of articles column.
Of course, this is a cosmetic issue only. The user can just resize the list of articles column to make it work again.
