Like this memo to participate in 100 000 sat giveaway. Winner announcing: 2018.06.27 21:00UTC (or later). 335DC9CB6DF04990BC36A765178904493A6F7F8E671F85D24500D311601222F1
It's a way for him to prove he didn't change the rules after making his post. The hash of the rules is that string, but you can't work backwards from that, you can only verify later.