If you double-click a word in the editor, and then move the mouse before
letting go of the button (eg, PRESS RELEASE PRESS MOVE RELEASE), then the
highlighting on the word disappears and the cursor starts blinking again,
but as far as gtkhtml is concerned, the word is still actually selected.
Eg, if you hit Backspace, the whole word will be deleted, not just the
character before the cursor.

This happens if you move the mouse even a single pixel, which is really easy
to do accidentally when double-clicking