Partially duplicated by JENKINS-18947 (in the part that both issues ask to notify the user who started a build).
With a look at this from 2019, note also that recently there were Jenkins core changes to promote running jobs as different Jenkins accounts, not just as "System". In relation to this story, make sure to NOT notify jobs started automatically, perhaps whether as System or not (the BuildCause's should probably allow to differentiate that), probably including non-human re-runs of such, although should probably it should notify a person who started a parent job that triggered this one with IM notifications enabled.
changed issue type and summary