Yesterday I performed the migration of Inkscape's bugs from SourceForge.net to Launchpad. This was a full import of all their historic bug data – about 6900 bugs.

As the import only had access to the SF user names for bug reporters, commenters and assignees, it was not possible to link them up to existing Launchpad users in most cases. This means that duplicate person objects have been created with email addresses like $USERNAME@users.sourceforge.net.