The reduplication of the adjective represents the deepening of degree, therefore, gāogāoxìngxìng 高高兴兴 has already owns the meaning of what ‘the evaluative marker + adjective’ expresses. So it is allowed to say both hěn-gāoxìng很高兴 and gāogāoxìngxìng高高兴兴, but not allowed to express the repetitive meanings.
