Bug in "comm" command

[fditolla]

Hi,
I have isntalled the CYGwin suite ant the command 'comm' that is provided
(man page is laelled 2.0.21) is misbehaving when file f1 contains a set of
rows and file f2 contains a subset of it as far

As I unedrstand comm should work as follows: if

f1={
x
y
z
}

f2={
x
}

the three coloumns should be

1    2    3
           x
y
z

Hence

comm -12 f1 f2

should suppress col 1 and 2 and should produce a file with one line
fout={x} and instead it produces and empty output.

comm -13 f1 f2

should suppress col 1 and 3 and should produce an empty file and instead
it produces a file of one line fout={x}.

comm -23 f1 f2
should supprss col 2 and  3 and produce a file of two lines
fout={
y
z
}
and instead it produces a file of three lines
fout={
x
y
z
}

At least this is waht I understand and what I get on an HP UX system.
best regards
Franz