It looks like other Bitbucket Branch Source folders that consume a global library in Bitbucket, it also notifies that commit of that repository of failure or success (sometimes?).

Jenkinsfile

@Library('myLibrary@0.1.0')

node {
  sh 'exit 1'
}

that is a contrived example, but see the attached image for multiple notifications that don't stem from this repository that seem to come from other consuming organization folder jobs.