If it used to handle the signal and then re-raise it, why doesn't it now set its flag and then re-raise the signal?  (I also don't understand why the API isn't that the application takes back the signal handler if it needs it if it is using readline, but I'm not familiar enough with signal handling in applications to really judge that, I suppose.)

However, we certainly understand the issues with doing too much in signal handlers, so if that ship has sailed I guess we'll just have to deal with it.