[fenomas]

This is such a facially bizarre thing to contest. They got a Japanese NCO to write the text, and presumably copied it as he wrote it. Why imagine that the NCO wrote it vertically and the soldiers horizontally? Likewise the article doesn't suggest that anyone thought the sign was written by a native speaker; why even imagine that's a requirement?

I mean, consider this in the abstract - the objections you're making here rest on the implicit assumption that you know more about the realities of life in a Japanese POW camp than TFA's author. (After all, if he fabricated the story about the sign he'd obviously fabricate it so as to be consistent with his experiences in the camp.) Do you really think that premise is more likely than the alternative - that TFA's extremely brief telling of the story simply doesn't include whatever details would answer your objections?

[kybernetikos]

Most likely the circumstance they got the Japanese NCO to write the text in was a conversation about learning Japanese and how to write it too. Nobody is deliberately trying to stop them from learning to write, they are most likely in favour of it, the trickiness was just around avoiding the Japanese running the camp from noticing their interest in workshops specifically. If stroke order is important in this context then I expect the Japanese NCO showing them the characters would have told them and explained the proper order.

[fenomas]

I don't think the writing matters a whit.

The only premise the story depends on is: that the camp guards saw the workshop and took it for granted that it was approved by somebody, since it was orderly and operating openly. If you accept that, it doesn't matter if the sign was amateurish or even upside-down - it would just look like something the workers had been told to make, or had made themselves to test the tools or to pass the time.

A bunch of posters here seem to be imagining that the sign was the lone keystone of the ruse, and that for some reason it needed to look like it was written by a native speaker or else the whole plan toppled. But nothing in TFA suggests that, it just says the sign was one of several things the POWs did to make the whole setup look like it had approval to be there.