Composed text from Input Method Editor doesn't show up sometimes

When the composed text from the IME is at the end of a paragraph, but there is a TextSpan that contains the last text in the paragraph (that is, the parent of the TextNode is a TextSpan, whose parent is then the Paragraph) then the composed text is not painted, even though the caret moves the correct amount. If there is no intervening TextSpan (that is, the TextNode is the direct descendant of the Paragraph) then the composed text is painted correctly.