Being a combination of AO or BO does have an effect on the secretion of H, the actual "O antigen." (H is a precursor to A or B)

This is dependant largely on whether the AO or BO in question is an ABH "secretor" versus a "non-secretor."
AO or BO secretors would secrete more free H antigen in their secretions than the corresponding AA or BB secretors. Theoretically, this would imply that O(H) specific lectins or antibodies would, to some degree, react in AH and BH secretors.

Whether or not other characteristics are also displayed is unknown.

However, it is not true that AO (or more acurately AH) secretors secrete anywhere near the amount of H as O secretors. Most of the enzyme systems responsible for the elaboration of blood type antigens (the transferases, for example) are under Mendelian (ie dominant/recessive) type control; so even though the AO or BO individual was technically only "half as much" an A or B as an AA or BB, probably greater than 95% of their enzyme activity is switched by the dominant A or B gene to the production of that respective antigen, versus H.