In my paper, just published, Biblical Formatting, I suggest that just as a modern author will use repeated keywords to indicate a bullet effect, so will the Biblical Author use repeated keywords to indicate a bullet effect. In other words the Biblical reader perceived repeated keywords the same way the modern reader perceives bullets. In both cases the bullets indicate to the reader an unspecified contrastive emphasis between the bullet items.

There is an important implication to this that is often overlooked. The unspecified emphasis implied by bullets as used by a modern author is perceived as the intended meaning of the text - it is not exegetical, though, since the emphasis is unspecified it is semi-conjectural. In a similar manner the unspecified emphasis implied by repeated keywords should be perceived as the intended meaning of the text - not as homiletic fancy.

Let us apply this bullets - repeated keywords analogy to verse Ex18-10 which discusses how God saved the Jews from Egypt: And Jethro said: 'Blessed be HaShem,
• who hath delivered you
  • out of the hand of the Egyptians, and
  • out of the hand of Pharaoh;
• who hath delivered the people
  • from under the hand of the Egyptians.
We have used modern bullet notation to hi-light the contrastive emphasis connoted by the repeating keywords. The Rashi comments explain this contrastive emphasis: God saved the Jews from
• the hand of the Egyptians--a difficult nation
• the hand of Pharoh -- a difficult leader
• under the hand of the Egyptians -- a difficult slavery.
Here Rashi sees the bullet items as indicating multiple dimensions of difficulty: Difficulty in the a) nation, b) leader (Pharoh) and c) the intensity of servitude.

Advanced Rashi: It is important to emphasize what Rashi is doing as well as what he is not doing. Rashi is not being picky on Biblical words -- Egypt, Pharoh, on-under the hand. Rather, Rashi is sensing broad connotations of unspecified emphasis implied by a bulleted structure. It seems to me that this is the most plausible way to understand these Rashis.