> Does the molding actually serve a functional purpose?  There are posts from the archive suggesting they are decorative only.

Sheesh, couldn't you ask a question where everyone agrees upon the
answer, like what the best tires are?
The practical upshot of past discussion on the matter of window rubber
trim is as follows:
-Subjective examination of junkyard Vanagons suggests that removal of
the trim makes pushing the window out easier. (could push glass out
without trim, couldn't with trim in place)
-Seat of the pants physics estimates based on descriptions of the
above suggest that decelerative G forces necessary to achieve
comparable forces would render the issue of windshields popping out
"the least of your worries".
-Official VAG supplier of relacement rubber unequivocably states that
the trim pieces are not designed to perform any fixative service and
are purely decorative
-Anecdotal evidence suggests that vehicles with old and/or dry rubber
may experience leakage upon removal of trim due to a slight reduction
in rubber compression.

Verdict: Trim adds stiffness to rubber which may prevent leaks, but
removal is not a safety issue. If you're removing it and wish to take
the belt-and-suspenders approach, fill the channel with appropriate
size screen spline material.