I think those are payouts from forrestv's mining operation, not donations. (I could be wrong.)
Block 164153 and 164207 were mined on the the old chain (old miners)
I think block 164142 was mined before the chain split, but im not sure about this block.
The new block chain (only new miners) didnt find a block since the chain split.
I received payout for all three of those blocks. I'm using the latest P2Pool.
The --give-author param you can specify goes to that address (default 0.5).
I was running a old version and also received payout from all three blocks.
p2pool showed very little overall pool hash rate and difficulty of ~4, so I guess I was on a split chain.
I just updated my p2pool ( also re-downloaded p2pool chain ) and "payout if" was way below what i received.
I have no idea what happend there.
edit:
The split chain probably still had shares from before the split.