Display of custom checkbox field values is broken on event confirmation page

The display of values selected on custom checkbox fields is broken on the event confirmation page:

Add a new custom field - Alphanumeric CheckBox
Create two options:
Label 'Int 1', value '1'
Label 'Int 2', value '2'

Add a second field - Alphanumeric Checkbox
Create two options:
Label 'Text one', value 'One'
Label 'Text two', value 'Two'

Add these fields to a profile, and add the profile to an event. Register for the event selecting both options on both fields. Notice that the display is broken:

Expected: 1, 2; One, Two
Actual: 1,1; ,

The cause is the horrible ghastly CRM_Event_BAO_Event::displayProfile method, which seems to be some toxic legacy code. Ideally we need to replace that whole method. A short term solution would be for it to handle checkbox options correctly, and add it to the toxic code list?