It seems that builds are only triggered by post-commit-hook if the previous build was stable. Starting a commit-hook after a stable build will work as expected and result in:

_Feb 02, 2017 9:19:02 AM INFO jenkins.scm.impl.subversion.SubversionSCMSource$ListenerImpl onNotify
Received post-commit hook from <uuid> for revision <rev> on paths <path>
Feb 02, 2017 9:19:02 AM INFO jenkins.scm.impl.subversion.SubversionSCMSource$ListenerImpl onNotify
No subversion consumers for UUID <uuid>
Feb 02, 2017 9:19:02 AM INFO hudson.triggers.SCMTrigger$Runner run
SCM changes detected in <job>. Triggering #17
Feb 02, 2017 9:19:40 AM INFO org.jenkinsci.plugins.workflow.job.WorkflowRun finish
<job> #17 completed: SUCCESS_

As soon as the previous build isn't stable or doesn't exist the commit-hook seems to be noticed but there aren't any connected projects found:

_Feb 02, 2017 9:25:28 AM INFO jenkins.scm.impl.subversion.SubversionSCMSource$ListenerImpl onNotify
Received post-commit hook from <uuid> for revision <rev> on paths <path>
Feb 02, 2017 9:25:28 AM INFO jenkins.scm.impl.subversion.SubversionSCMSource$ListenerImpl onNotify
No subversion consumers for UUID <uuid>
Feb 02, 2017 9:27:11 AM WARNING hudson.scm.SubversionRepositoryStatus$JobTriggerListenerImpl onNotify
No subversion jobs using repository: <uuid> _

Additionally the changelog of failed builds is empty. There's also no information about the used scm-revision.
Furthermore it is not possible to trigger multiple projects via the same commit-hook.