Common denominator thought as restricted to persons seems the problem to perceive the information in the text. Common denominator ascribed in the Ayah is "Ma Anzalna" and its purpose is restricted by words Illa tazkeratan. [Qur'aan is Takeratun: 74:54]
The negation in 20:2 + "exception" in 20:3 together are the common dominator.
If one reads 20:2 without the "MA" and instead of the "ILLA" a "WA" (in 20:3) then it makes it easier to understand what the common dominator is.
For convenice: What is common denominator - ascription in this sentence: I saw the travellers except their luggage. [In Arabic it is called Disjunctive Mustathna- travellers and luggage are different]
It is seeing informing: I saw the travellers only, I did not see their luggage.
I am not sure "common denominator" was a good choise of words from me but inshaAllah you understod what I meant.
In the sentence you mentioned, the "common denominator" is: (The travellers + Their luggage)
You were expecting to see them (The travellers + Their luggage) as a whole, BUT you saw only the travellers, that's why you used "except".
And yes I understand what you mean that they are of different kind, but there is alwas a relation.
Pronoun "Ka" in prepositional phrase "upon - to you" and pronoun "Anta" concealed in the second person subjunctive verb is exclusively for the Messenger Muhammad [Sal'lallaa'hoalaih'wa'salam]. Qur'aan was sent to him: see 47:2.
If we hold only The Quran as our judge then it is very hard to proof this, there are a couple of things to ponder on.
-- If Allah wanted to use the name "Mohammed" or "messenger" in the ayaat then He for sure would be capable to do it, just like how he calls Musa several times by his name, when He calls him.
But He did not do it for a reason. So in my opinion a good translator should at least not put words in places when they are not there in arabic, or at least put it in brackets or as footnote, but not like how you did it with the word "messenger" in 20:2. It is there without brackets so someone who reads it without knowing arabic might think that in arabic the word also exist in that verse.
-- If the ayaats were like this:
20:2 We did not send down to you the Qur'an so you may suffer O Mohammed (or any specific name of a person).
20:3 It is but a reminder for he who is concerned.
Then the relation between 20:2 and 20:3 is making no sense at all. That is why imo no name is used but simply "you".
-- about 47:2, first you have to proof to what the red part is referring to, Allah has anazala a lot of things:47:2 And those who believe and do good works, and believe in what was sent down to Mohammed, for it is the truth from their Lord, He cancels for them their sins, and relieves their concern.
and after that you have to proof that the "you" in 20:2 is referring ONLY to the Mohammed of 47:2.
With proof I mean only Quran ayaats.
-- please take a look at the next ayaats:2:136 Say: "We believe in God and in what was onzila to us and what was sent down to Abraham, and Ishmael, and Isaac, and Jacob, and the Patriarchs, and what was given to Moses and Jesus, and what was given to the prophets from their Lord; we do not make a distinction between any of them and to Him we submit."2:231 And if you have divorced the women, and they have reached their required interim period, then either you remain together equitably, or part ways equitably. And do not reconcile with them so you can harm them out of animosity; whoever does so is doing wrong to his soul; and do not take the revelations of God as mockery. And remember the blessings of God upon you, and what was anzala AAalaykum of the Book and the wisdom, He warns you with it. And be aware of God and know that God is knowledgeable of all things.6:114 "Shall I seek other than God as a judge when He anzala ilaykumu the Book fully detailed?" Those to whom We have given the Book know it is munazzalun from your Lord with the truth; so do not takoonanna who have doubt.
There are many many more, I see no exclusivity for Mohammed for something that is anzala from The One who has created the earth and the heavens above.
Also note in 6:114 the changing in perspective, who is the "I" and who is the plural "you", why this change?
anyways we are going oftopic, but at least I gave my opinion about which translations I like and which not