I've never heard of Adorno or the other guys above, but since you mentioned postmodernism I know the gist of it (as far as identity is concerned). Taking the 'other' the same as oneself, if I understand you right, is smth close to that - the individual becomes decentered (from Center to Otherness) or lacking any unified self; identity is thus an emerging concept, a mozaic of roles and experiences, not an absolute concept.