Can't undo text effects for the private message

When creating a new private message can do such text effects as: Bold, Italic, Underlined, Stricted, Highlight.( All effects are only seen in Preview)
But can't undo them - new pressings on the buttons of text effects for discharging the effects only add unapprehensive symbols around my text.
(Preview of my message still the same - with all these effects)

PrintScreens in attachments.