Apparently YC thought that capitalizing "SAFE" was inconvenient: http://blog.ycombinator.com/announcing-the-safe-a-replacemen...

For what it's worth, I think this causes more confusion than it's worth.

The article is written from a place (what Eric Evans calls a 'bounded context') where the term is so well known that people just use it as a common noun. But crossing into the HN context that's no longer true, so we've uppercased it for you above.

(I almost said improper noun but apparently that's like land seahorse.)