"A speaker will be judged on the basis of how she treats her weakest listeners"

 Who said that ? :-) 

 More seriously... Don't forget to repeat the key words for the distracted, the hard of hearing and the foreigner. 

 It often happens  to me that I miss a word. Sometimes I just don't understand it because the speaker speaks too quickly, or with an English accent - There is nothing wrong with having an English accent! It's just that sometimes I don't get it. 

 It may also happen that something the speakers says triggers a chain of thoughts... (Whoa! I would never have seen it that way! .....)  ...and I miss the next bit. If the next bit was a key moment of the speech, and if the speaker doesn't repeat, I am out... 

 Public speaking means that you are talking for the weakest links. Some don't hear well, others don't understand quickly. If only the 180 IQ genius in good health sitting in the front row gets it, the job is not done...  

 Don't hesitate to repeat the essentials as your speech goes along !