Also this particular plugin has a longer history, because you first tried to publish it via Felix in the context of https://issues.apache.org/jira/browse/FELIX-6019?page=com.atlassian.jira.plugin.system.issuetabpanels%3Aall-tabpanel which triggered also a longer discussion. The outcome is not obvious to me, but from a high level it seems that the header is actually correct and should not be removed, it only needs to be removed from Karaf. But IIUC the newest Karaf has introduced a config option to be able to deal with that header correctly as well. Also I still think if the plugin is valuable it rather belongs to bn or Felix but not to Sling.
Maybe you can shed some more light on this.