How to reproduce :

• I created a new tag "WITHOUT_TITLE" like this

  <tag id="SPECIAL_CONTENTS" target="CONTENT">
  		<label i18n="true">SKIN_BO_TAG_SPECIALCONTENTS_LABEL</label>
  		<description i18n="true">SKIN_BO_TAG_SPECIALCONTENTS_DESCRIPTION</description>
  		
  		<tag id="WITHOUT_TITLE" target="CONTENT" private="true">
  			<label i18n="true">SKIN_BO_TAG_SPECIALCONTENTS_TAG_WITHOUT_TITLE_LABEL</label>
  			<description i18n="true">SKIN_BO_TAG_SPECIALCONTENTS_TAG_WITHOUT_TITLE_DESCRIPTION</description>
  		</tag>
  	</tag>

• I added this tag to a content
• I previewed > all was right
• I removed this tag
• I previewed > the tag seemed to be still linked to the content so I went again on the tag panel > the checkbox of the tag was still checked
  > there is no way to remove the tag.