How can I suppress the presentation of discount codes in receipts?
I've edited the message template and used a truncate filter on the $line.label to hide the discount code. Something like this is what I've done:

&lt;td {$tdfirstStyle}&gt;
{* Truncate $line.label to hide a discount code if present for certain event types *}
{if $event.event_type_id == 12}
  {if $line.html_type eq'Text'}
    {$line.label|truncate:7:"":false:false}
  {else}
    {$line.field_title} - {$line.label|truncate:7:"":false:false}
  {/if}
{else}
  {if $line.html_type eq 'Text'}
    {$line.label}
  {else}
    {$line.field_title} - {$line.label}
  {/if}
{/if}
{if $line.description}
  &lt;div&gt;{$line.description|truncate:30:"..."}&lt;/div&gt;
{/if}
&lt;/td&gt;


I think for this to work cleanly you might need to have Fee Levels with names of similar character count. There might be some other output filter that would work better than truncate... I recall trying to use some sort of RegEx filter that didn't work.