I seem to remember non-blocking io with named pipes was unreliable, in the sense that the test suite of whatever-it-was (memory is reeealy sketchy, this was tens of years ago) would fail randomly often enough that we had to throw the easy solution away and do actual networking.

A bit like the .signature named pipe from fortune thing, where sometimes you got two signatures and sometimes none? Anybody remember that?

Is this what you're referring to?

signature file can't be a named pipe (or /proc/uptime) https://bugzilla.mozilla.org/show_bug.cgi?id=62993

can't attach signature from pipe (fifo) https://bugzilla.mozilla.org/show_bug.cgi?id=163831