Many languages distinguish between inclusive and exclusive first-person plural pronouns (“we”). The inclusive “we” specifically includes the addressee (“you and I and possibly others”), while the exclusive “we” specifically excludes the addressee (“he/she/they and I, but not you”). This grammatical distinction is called “clusivity.” While Semitic languages such as Hebrew or most Indo-European languages such as Greek or English do not make that distinction, translators of languages with that distinction have to make a choice every time they encounter “we” or a form thereof (in English: “we,” “our,” or “us”).
For this verse, translators typically select the exclusive form (excluding Moses).
Source: Velma Pickett and Florence Cowan in Notes on Translation January 1962, p. 1ff.
Following are a number of back-translations of Acts 7:27:
Uma: “But the one who had hit his companion pushed Musa and said to him: ‘Who raised you(s) to become a leader who decides our (excl.) matters?” (Source: Uma Back Translation)
Yakan: “But the man who did the beating pushed Musa and said, ‘Who gave you authority to be leader over us (excl.)? Why should you be the one to judge us (excl.)?” (Source: Yakan Back Translation)
Western Bukidnon Manobo: “However the one who was in the wrong would not listen. He pushed Moses and said, ‘Who gave you the authority to be Datu over us?” (Source: Western Bukidnon Manobo Back Translation)
Kankanaey: “‘But the one who was-at-fault (lit. sinned), he up-and-shoved-at Moses saying, ‘Is it indeed-the-case (sarc. RQ) that you (singular) have authority to rule-over and judge us (excl.)?” (Source: Kankanaey Back Translation)
Tagbanwa: “But he was pushed back by one of them who was picking-a-fight and told, ‘Expl.! Who set you up as our (excl.) leader and judge?” (Source: Tagbanwa Back Translation)
The name that is transliterated as “Moses” in English is signed in Spanish Sign Language in accordance with the depiction of Moses in the famous statue by Michelangelo (see here). (Source: John Elwode in The Bible Translator 2008, p. 78ff.)
Another depiction in Spanish Sign Language (source: Carlos Moreno Sastre):
The horns that are visible in Michelangelo’s statue are based on a passage in the Latin Vulgate translation (and many Catholic Bible translations that were translated through the 1950ies with that version as the source text). Jerome, the translator, had worked from a Hebrew text without the niqquds, the diacritical marks that signify the vowels in Hebrew and had interpreted the term קרו (k-r-n) in Exodus 34:29 as קֶ֫רֶן — keren “horned,” rather than קָרַו — karan “radiance” (describing the radiance of Moses’ head as he descends from Mount Sinai).
Even at the time of his translation, Jerome likely was not the only one making that decision as this recent article alludes to.