calls with comment attribute

In general R doesn't print the "comment" attribute of an object
   > structure(1:3, comment=c("a comment", "another comment"))
   [1] 1 2 3
but if the object is a call it prints it in an unusual format
   > structure(quote(func(arg)), comment=c("a comment", "another comment"))
   a comment
   another comment
   func(arg)

What is the rationale for the special treatment of calls?

Bill Dunlap
TIBCO Software
wdunlap tibco.com