The word "nothing" and the word "noting" were pronounced alike in Shakespeare's day.  "Noting" or "observing" has a great deal to do with the play since much of the play is about appearances.  In the beginning, Beatrice and Benedick appear to be enemies, but since they so easily fall in love with one another, it's pretty clear they each really have deep feelings for the other that they cover up with their verbal gibes.  Following that idea, it is with false information that Beatrice and Benedick both admit their affections for one another.  Thus another example of deceiving appearances.  Don John uses deception, or faulty noting, to weave his nastiness.  He acts like he thinks Claudio is Benedick at the masquerade when he really knows who it is he is talking to.  Then he has Borachio get Margaret to the window while he makes love to her so that Claudio and Don Pedro might confuse Margaret for Hero thus discrediting Hero.  Even the masquerade party itself is an example of faulty noting.  Beatrice talks with Benedick, acting like she doesn't know it is him, when she really does.  That the people are covering their identities with masks is another example of deceptive appearances.  So, there really is a great deal of fuss made over perception, or "noting" in the play.  And since most of the appearances are false, there is "nothing" really to get upset about.  You have to give a lot of credit to that crafty Shakespeare who loved wordplay!