If the gnome-utils package (which contains gnome-dictionary) is not installed, the deskbar-applet will still show the dictionary plugin as present and allow the user to enable it. However, when enabled it does nothing since gnome-dictionary is required for the plugin to function. It would be nice if there could either be a) a warning message displayed when attempting to enable the plugin if gnome-dictionary is not present, or b) a check for the 'spell' use flag in the deskbar-applet ebuild that would either install gnome-utils as a dependency or prevent the dictionary plugin from being built/shown.
Fixed with 2.16.2-r2, sorry for the delay.