Why is there a doubtful copyObject call in add_vars_to_targetlist

Hi,

I was debugging that when does the function _copyVar get invoked, and the
first hit for that was in the add_vars_to_targetlist. There I happened to
see the following comment:

/* XXX is copyObject necessary here? */

Further digging showed that this copyObject got added in the commit
5efe3121:

+ /* XXX is copyObject necessary here? */
+ rel->targetlist = lappend(rel->targetlist,
+ create_tl_element((Var *) copyObject(var),
+ length(rel->targetlist) + 1));

This copyObject still exits in the current code. So I was wondering if the
comment question still holds good and why the question there in first place.
To make a new Var object, copyObject seem to be the right choice, then why
the doubt?

Regards,
Neha