The tags to ignore when looking for untagged nodes seem to be defined in [UntaggedNode.java function visitKeyValue()][1]. Currently they are:
- tag fixme=*
- tags starting with
- note, comment or description
- created_by or converted_by
- watch
- source
I'm not sure if you can disable this behavior. However you can explicitly add tags you are searching for, for example by using "untagged or fixme or note".
[1]: https://josm.openstreetmap.de/browser/josm/trunk/src/org/openstreetmap/josm/data/validation/tests/UntaggedNode.java#L62