Yes, there are other ways to bring trains to a halt or to derail them. Even so I think it is irresponsible to spread such information further than it has to go, especially on a site called 'hacker news', and even more so in a thread where people are openly arguing that insecure systems should be replaced by more secure ones. Rail infra is not as easy to update as your average web based project and keeping such information out of the hands of would-be experimenters can only be good. No downside, possible upside: easy decision.