I will have to agree with Mallory, that 20 is better than 10, since some people post detailed replies about something, as exposed to someone only posting one-line sentences in a repliy.
Similar vein, how long before we can give rep to the same person? I just got a noti saying I needed to spread some around before giving it to the same person. Maybe it's becaus I'm a junior member.
I think for that it might be ten. I tried to figure it out before, but stopped paying attention before I could actually confirm it.
It's only a matter of time where someone will say, 30 is better than 20. To be honest i dont know why we even need rep. But i understand people wanting to say thanks and the likes.