What would I edit in order to keep the date/time from appearing on a sticky post? Unfortunately, the post-byline seems to be a div universally used in any kind of post. (I feel like I should be placing php code somewhere to force the date/time not to show if the post is sticky, but don't know where to place it...)

I am using the latest version of Atahualpa.

Edited: The solution is in this thread:

http://forum.bytesforall.com/showthread.php?t=917

(substitute post-byline for post-footer in their example.)

And what do you consider to be the latest version?? 3.4.9? 3.5.4?
You could use CSS to set the display to 'none'