When a word is selected and you right click on it and browse to Related Words, and click a related word, the word is not replaced. Rather, the new related word is inserted within the characters of the previous word, resulting in something like
exceptiexceedingonally
instead of exceeding replacing exceptionally, and
afposteriorter
instead of posterior replacing after.
The place where the new word is inserted depends on where within the old word you click your mouse pointer.