Sherlock stood still, neither pushing him away nor pulling him close. This wasn't exactly how he thought things would go, not with the day starting so manically with knives and threats of suicide. It was never safe to assume such gestures meant anything when it came to the sociopath but there were hints throughout that Sherlock had the power of life and death over the man with nothing more than whims to orchestrate his demise. Moriarty was desperate for his attention--maybe even affection. Denying him risked dangerous behavior; obliging was just as potentially risky. So he stood still, not so shocked as last time to now consider certain elements of the experience.