Maybe I misunderstand. Let's say I have 5 sockpuppet accounts. I send 1 BCH in tips from A to B to C to D to E and back to A. It only cost me 1c in tx fee or so. How do you stop this?
You could simply discard or discount votes from people you don't follow.
I think algorithms based on your own circle of trust is going to be the way forward. There could be a market for the most useful memo algorithms as well as human selected follow lists.
I think eventually we'll get bots popping up that comb through accounts and weed out circular tipping, vote gaming etc.. They can then publish the info for tips.