Thanks for the reply Bryan. I found a way to add a comment/activities by gliding approval table. To achieve this, I've created a run-script activity right after the approval activity. Once the approval request in place, my script run, look for current item's request and add a comment to let approval user know some information. Do you think this process affect anything or not a best practice to do? Thanks! 

Note: This is only related to one particular Catalog Item.