no heavy load on server ... Reply uses Rich Text box to write and "quick reply" uses simple html text area (which will definitely load quicker than rich text box).
But problem is, at first "text area" is displayed and user starts typing, and when other controls are loaded, control is refreshed.
I would suggest the technical team of PW to use some other Rich Text box like FCKEditor which is freeware as well to post reply. Its a excellent editor and you'll not have any need of Quick Reply even, it will load so quickly.
Thanks