Yeah, I'm fairly interested in hot loading. I also think that it is a killer feature for a language (especially game development). No, I haven't tried to use hot loading in any real Nim program I've done. I wrote that article after reading another article about a game dev who said he used it in lieu of spending the time to integrate a (slow) scripting language.
When I was working on mine, I didn't experience any SIGSEGV crashes. I was working on a Linux machine; though I'm not sure if that makes much of a difference.
I haven't play with the RTL library at all, or the GC too much. It would be best to as Araq or dom96 what's going on there.