Holger Levsen
Holger Levsen has been contributing to Debian for more than a decade.
In these years he has been a DebConf organizer and founded of the DebConf videoteam, which produces the video.debian.net archive.
Since 2009 he has been running piuparts.debian.org, to make sure all Debian packages follow policy.
As this still didn't satisfy his desire for quality assurance he set up jenkins.debian.net in 2012 which now runs over 600 jobs testing various aspects of Debian.
Then, in 2014 he created 14 jenkins jobs to produce reproducible.debian.net.
He is located in Hamburg in northern Germany at least some of the time.