Sorry, but I'm not like GfK in terms of how willing you are to come up with alternative theories to why someone would say someone else has died.
Occam's Razor? Which is the more likely scenario? That he posted a fake "death" post, or that his sister, presumably stricken with grief over the loss of her brother, took the time to write down a sappy note to a bunch of complete asshole strangers on an Internet forum, she would probably not even be aware her brother posted in?He faked it.