ls gets confused by IFS environment variable

[Elmar Stellnberger]

LS gets confused as soon as the IFS environment variable only contains
control characters.

# IFS contains an NL only:
> bash
> IFS=$(echo -e "\n")
> ls
/bin/ls: Ungültige Option --
„/bin/ls --help“ gibt weitere Informationen.

# IFS contains TAB,NL and SPACE:
> IFS=$(echo -e " \t\n")
> ls -1
bin
boot
dev
...

Strange! There is also nothing about IFS in the man or info pages of "ls".
Why has IFS an influence on "ls" at all?