You can't reverse a confirmed transaction. All they can do is contact the miner/mining pool, prove their identity by signing a message with the sending key, and ask pretty-please-can-I-have-my-bitcoin-back? There have been some major cases where that has been done (kudos to the miners!), but it gets more tiresome every time this happens and I can understand if they draw the line somewhere.

I'll say it AGAIN - the authors of wallets need to hardcode limits on the transaction fees to flatly prevent someone from accidently plugging in an absurdly high fee. If someone ever does want to send something with a huge fee let them use a custom wallet or tool to do it. The rest of us don't need the "ability" to send a transaction with a fee of higher than, say, 0.1 BTC.