So you're saying there are no obvious ways people do this to themselves? What about my two specific questions about things that might try to talk to STDERR? Would either of those kill the daemon?

The whole code is up over 700 lines at this point, which seems entirely excessive to ask people to grope through. I'm reasonably certain that the simplest case will not reproduce the problem (that would mean Proc::Daemon and Log::Log4perl were incompatible, and there's lots of evidence of people using them together). So I'm working down, rather than up, in this case, and that's going to be slower.