CiviEvent custom data missing on confirmation page
Yep, that is a proper bug.
CiviCRM has a public issue tracking system, it's on https://issues.civicrm.org.

This bug was already found, see https://issues.civicrm.org/jira/browse/CRM-17129
It's solved in 4.7

If you really need it on 4.6 you can also find the patch there and try it on a test version of your site. No guarantees, so make sure you are not doing it on your production site.

If you would find another bug in the future and it can not be found via a search on issues.civicrm.org, you can help the whole community by creating an issue over there.