I noted that the opera 7.23 ebuild is dependent on either lesstif or openmotif. However, if --deep is passed as an argument to opera, it detects that lesstif needs to be emerged. Given that the RDEPEND doesn't specify lesstif or openmotif versions, maybe it makes more sense for it to depend on virtual/motif.
This is a portage bug then, opera won't depend on virtual/motif since this will be dropped soon. There are several bugs about a broken --deep option.