Membership signup overwrites individual contact as Organization instead of creating new Org

See http://civicrm.stackexchange.com/questions/10636/turn-deduping-off

I copied code in from 4.7.3 in CRM/Contribute/Form/Contribution/Confirm.php which resolved this particular issue (see the above Stackexchange link), but now a new Org is created with every renewal.

There is some commenting in the code I changed that indicates this may have something to do with CRM-15182

Steps to replicate:

1. Create drupal CMS user w/attendant Individual contact
2. sign user up for on-behalf membership, give the new Organization a name that is the same as the display_name of the individual
3. membership process overwrites the individual instead of creating a new Organization, sets its type to Organization, omits the rest of the on-behalf fields (address etc.)