If this is a workflow approval task then you will can use the comments section.
If not then you can call the request task, after the user modification task to record a request reason.
IF you need guidance on the above, you can always open a support ticket, and it looks like you might.
When you open the support ticket, please include:
IM version
if connected to SM, SM version
User store type and version
a screen shot of what you have configured so far, and an explanation of what you are trying to do.
Thanks,
Bill Patton