The document ChangeListener? does not seem to be added to the first file in tab group when that file has syntax highlighting. The "*" change symbol does not appear when the user starts typing, and if the tab is closed without saving, no warning appears.
If additional files are opened in that tab group, these tabs have change listeners applied. If all files are closed in the group and then a new tab is opened, this new tab will not have the change listener. The missing change listener seems to have to do with being the only file newly opened in a tab group.
[Issue report ported from Trac.]