Sounds as though the SMOP is more trouble (after all there are other enhancements not yet actualized) than requiring writer(s) (even "time after time. world-without-end....") to clear the first msg; ^A, del w/cursor in msg entry box.

P.S. A box labeled in line with hotchiwawa's suggestion above -- clear or reset -- would be less subject to misunderstanding than erase.

Perhaps more worthy of the labor: code to chew one's lunch to save personal effort?