I think it's mroe keepign an eye to the future then the present. Just like the fore fathers and the constitution . Sure, now I think everyone won't abuse it, but say the baord grows and grows. There's no way for the moderators to police everyone in the use of high fives, and there is no guaruntee that new posters when influxed into the board won't change the landscape of how high fives are viewed or used.
I think by staying cautious now, and implementing the system that is limited but even handed, the results will be good. Even if it is approached again later, it can be expanded, but as far as bringing in new systems, I think baby steps are an essential part of proportioned and mindful growth.