Etherum was really nice to the guys who made the DAO that was hacked? What determines when a cryptocurrency decides to cooperate to undo a hack? Does it come down to connections between those affected and the cryptocurrency management?
Even Bitcoin has forked to roll back transactions, though not recently, and in the past only due to protocol vulnerabilities, never 3rd party software like the DAO or a hacked exchange.
I’d be wary of mature cryptocurrencies where this is feasible, especially if it’s "fixing" something that doesn’t affect the majority of users.