The J branding under the eye, the psychotic tattoo self imagery, the missing teeth as if somebody beat the face off of him with a crow bar? I think your not looking at "THE" Joker here. I think your looking at Robin turned Joker. The tattoos to me are reflective of what Robin would have witnessed in his final momenta. Laughter, a constant grin... And he himself is damaged and constantly tormented hence being branded with the J... Almost like spoiler in spoiler. But i wouldnt commit just yet on it being Jason Todd who is the dead Robin... Id say for audience connection it will be either Dick or Tim.