Methods 'nosymessage' and 'send_message' in
'roundupdb.py' do not create a system message anymore
if no message id is passed to those methods. The emails
will be send as if created by user admin (admin added
the comment:) and user admin will receive a copy of the
email if 'messages_to_author' in 'config.ini' is set to
'yes', while he might not be the author at all.

This behaviour is the result of code at line 183
(nosymessage) and line 277 (send_message) where the
author id is set to '1' (admin) if 'msgid' is 'None'
(the line nubers are valid for
roundup 0.8.2).

Logged In: YES 
user_id=6405

I'm not sure I follow. Is the admin user the only one on 
the nosy list? 
 

Logged In: YES 
user_id=1080231

I agree, the summary isn't that clear. Well let me give it
an other try.
In the past when a email was send to the nosy list, it would
either send a message starting with '<user> added the
comment:' or with 'System message:'. The first one was send
if a message was added to the issue. The last one was send
if no message was add to the issue but some property was
changes (this was only the case if the nosy detector was
changed). In that case no *msgid* was passed to the
*nosymessage* method. Currently this last behavior is broken
due to the lines mentioned in the summary above. If *msgid*
is None, the author will be set to '1' (admin). The result
is that the message to the nosy list will start with 'admin
added the comment:' and not with 'System message:'.

I hope this will clear it up.

Logged In: YES 
user_id=6405

OK, I've fixed it now.