kqueue and libev

[James Mansion]

Any idea what the author of libev is on about here (from 
http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod):

unsigned int ev_recommended_backends ()

    Return the set of all backends compiled into this binary of libev
    and also recommended for this platform. This set is often smaller
    than the one returned by |ev_supported_backends|, as for example
    kqueue is broken on most BSDs and will not be autodetected unless
    you explicitly request it (assuming you know what you are doing).

and

|EVBACKEND_KQUEUE| (value 8, most BSD clones)

    Kqueue deserves special mention, as at the time of this writing, it
    was broken on all BSDs except NetBSD (usually it doesn't work with
    anything but sockets and pipes, except on Darwin, where of course
    its completely useless). For this reason its not being
    "autodetected" unless you explicitly specify it explicitly in the
    flags (i.e. using |EVBACKEND_KQUEUE|).

It looks like a decent library, but these comments seem unfortunate.  
Does anyone know what the author is concerned about?

James