SelfService ticket customization

I am looking for a solution to prevent system messages to be displayed to
SelfService users.
for example, when a user “takes” a ticket, the following messages is
displayed in the ticket log:
- Taken
- Priority changed to 10
etc.

I want SelfService users to see only corespondances to a ticket, not the
system messages.

is there a way to implement it?

thanks,

Motti.