>>4435796
>no trace of the person who repeatedly told Satoko she'd have no reason to keep her around if she didn't prove useful is left
In the anime, there's this quick scene right while Satoko is saying she only left the village by mistake. Konoha gets sad probably because she is getting scared that Satoko might try to go back one day. So she says that cruel line to hide her feelings and change the topic. In the beginning she probably meant it though.

>>4435795
>a distinct difference between destroying something indiscriminately and putting something back together exactly the way it was.
I don't dispute that. But I still think it'd be too impractical. If I were Marin I'd have Satoko leaf and unleaf 100 bolts to see if she'd get it right after a while. Then blindfold her and have her do it again once she got the hang of it. If that worked, I'd make her repeat these steps with bigger and more complex objects. If she got discouraged, I'd tell her the ultimate goal would be to turn Konoha's arm back to its original form.