Is there a way to leave out the Date and time stamp on all posts including comment posts in Atahualpa 3.5.3?

Corelle, try going to ATO>EDIT POST/PAGE INFO ITEMS>FOOTER: Single Post Pages, and then delete the following from the box there..

%date('F jS, Y')% |

Other elements in that field can be removed there as well if you wish.

Look at ATO>Edit POST/PAGE INFO ITEMS