Overlapping Payment Method/Comments section on checkout confirmation

When using auth.net CC payment the checkout confirmation page has the order comments section scooted up too high and it overlaps the bottom of the payment method block, making the text difficult to read.

What's extremely odd to me is that I can put in a fake CC number on the payment page, let Zen give me an error banner that it's an invalid card type, then provide a real card number - now when I go to the confirmation page, the layout is fine. But using a real card number the first time has things pushed up too high on the page.

Looks like the file that determines layout for this page is \includes\templates\my_template\templates\tpl_confirmation_default.php
?

For testing, I can add line breaks in there and they don't seem to show up - it's making it difficult to track down exactly where to make a change that will take care of the problem.

Any suggestions?

Don't have a "direct" answer, but the CSS that applies might have a part in this and that may be something in the template being used. Assuming you have either installed a template other than the default classic or not modified the classic template directly and are not seeing the issue while on the default/classic template, try the same process using the classic template to see if the problem persists.

Have tried the default template with the same results. It's almost as though a different template is being referenced in each case. When I make changes to the file (add some line breaks for example) those only show in the "correct" version but not in the incorrect layout.

It was the ajax version of the template (which appears to be new in 1.5.4). That was the version being used (in the default template folder) for each time the layout was incorrect. Making the same layout changes to that file that were already made in the other checkout confirmation template did the trick.