Bug in comm 2.0

Hello,

it seems that I have found a bug in comm 2.0. I have installed it from 
binaries under Debian 3.0.

The only difference between the files below is "Zeile3" respectively "Zeile3." 
(with a dot after). Calling
comm -3 file1 file2
says that not only "Zeile3" is different but also a few lines after.

By changing all the word "Zeile" to "row" in both files the behaviour of comm 
is different: only "row3", "row3." is shown as different.
I have done another change instead: I have changed the line beginning with 
"##" to "Zeile4" in both files: only "row3", "row3." is shown as different.

Making some other changes to the files give different results - somtimes 
right, sometimes wrong.

Is this a known bug? Or is there already a newer version where this bug is 
fixed?

With many greetings

Rolf Lucius

      *** file1 begins after this row ***
Zeile1

Zeile2

Zeile3

## setup-Unterprogramm START

setup()
{
while true
do
      *** file1 ends before this row ***

      *** file2 begins after this row ***
Zeile1

Zeile2

Zeile3.

## setup-Unterprogramm START

setup()
{
while true
do
      *** file2 ends before this row ***