You remove metadata the same way as you update it. First select a file from the file tree, then use the Metadata Table in its Assigned Metadata or All Metadata modes to select the metadata. If the metadata has a value assigned, the [R]emove button in the MetaEdit Controls becomes active. Click it to remove the metadata from the specified file. Other files remain unchanged, and the value still appears in the Value Tree.

If you remove metadata from a directory with children or from multiple files, a prompt presents several options. '[R]emove' removes the metadata from this file; 'Remove [A]ll' removes it from all remaining files; '[S]kip' leaves the metadata in this file and proceeds to the next; '[C]ancel' undoes any changes and cancels the action. Note that if you choose metadata that is not common to all the selected files, and you click the [R]emove button in the edit controls, the metadata will be removed from those files that have it. Those that do not contain this metadata will be unaffected.

This is a feature, not a bug! Even if you remove all references to a value, it doesn't mean you'll never want that value again. If you truely wish to remove the value as well you should use the Metadata Set Editor explained at the end of these help pages.