I have to disagree here. Not recommending signalfd for the mentioned use cases might be reasonable, just as reasonable as it is to use threads for a specific use case. For a single threaded non-blocking-FD using client/server signalfd removes the risk of doing too much in the signal handler and brings signals nicely into the event loop. This just happens to be 99% of the functionality I have to do.

I'd only use more than one signalfd if each signalfd only catches a specific signal. E.g. main context handles Sigterm and a background process library handles sigchld.