Info for the recode maintainer:
Thanks for the history lesson! Unfortunately, the solution chosen, namely to extend the functionality of glibc's implementation of POSIX iconv(3) in a surprising and confusing way, is of the sort where "now you have two problems".
This could be mitigated by documenting this extended behaviour of glibc iconv(3) (which I can find nowhere documented); I've filed bugs against glibc's manual[1] and the Linux man pages[2] for this.