Prior to AutoCAD 2004, if you pasted a block or inserted into a drawing the layer filters from the block would also come along. In some cases the drawings would get quite a few layer filters. Customers pointed out this problem and we changed the behavior in AutoCAD 2004. No longer do layer filters come in with blocks whether pasted or inserted. Also you can easily now select or delete all filters in the drawing. No more need for a custom LISP to do this.