Here is a sentence. I(i) enjoy yourself(i). Can we say "I" and "yourself" are coindexed but not coreferential?
Conventionally, coreferentiality is indicated with coindexing, i.e. coindexing is the notation for the theoretical concept. Since "I" and "yourself" are not corefential, this is an abuse of the notation; but yeah if you are trying to make a point about notation versus substantive facts about sentences, the words are coindexed, but not coreferential.