su and commands are no longer echoed

Hello,

I found your email address in the man pages for the su command that is 
shipped with Redhat Linux 7.2. First I have to say that I am not sure if 
the problem is with Linux 2.4.7-10smp. However let me describe the problem:

When I start a terminal emulator using xterm as a non root user (running 
under KDE), things are fine. The commands I typed are echoed 
immediately. But whenever I issue the su command, with or without the -l 
option, I commands I typed in are no longer echoed. However, the output 
of the commands is visible. That leads to the question: what setting is 
changed beside the uid with the command?

Of course it could be that is some funny code in xterm that decides to 
stop echoing when it finds out that uid is root. Maybe I will direct the 
problem to the xterm team as well.

Anyway I would appreciate if you could shed some light into this 
mystery. Thanks.

Bonminh Lam