Strange implementation of groups in SharePoint portal listings

Every portal area has a  “Portal Listings” list. A strange list that is managed in another way than all other lists. No properties can be changed or removed like with ordinary lists. The list cant be deleted like ordinary lists.The list is managed in a separate table in the database for optimal performance (no additional column mapping needed, all fields are available “as is” in the table).

For each portal listings list in an area groups can be definied. Initially there are three groups available that cannot be removed. The first group is “Highlight”, the second and third groups are “General” and “Expert”. All these groups can be renamed. Strange thing however is the “Highlight” group. You can rename the “Highlight” group, but in the “Grouping and Ordering” view you have the options in the actions list of a listing to “Highlight” a listing or “Remove Highlight” from a listing when the listing is in the “Highlight” group, even if you renamed the “Highlight“ group. When you choose “Remove Highlight”, the group is set to the second group. It is not possible to apply highlighting on top of a chosen group. This would be the best behaviour; highlight items in a given group. Strange behaviour...