If you entered text to search for a label and then tick that label, removing the text has no effect and will still apply that label.
Even though the text box is clear you can't clear the label field as it will apply the label selected in which you won't know because like stated in MBS-2168 it's not shown as the action being taken when entering as summarized when entering an edit note.
The duped issue here also mentioned that this can cause two labels to get added if you clear one and then select another.