Problematic pronouns and family dynamics
ויצא משה לקראת חתנו וישתחו וישק-לו וישאלו איש-לרעהו לשלום ויבאו האהלה
Moshe went out to greet his father-in-law [Yisro]. He bowed [to him] and kissed him, and one asked the other how they were doing, and they went into the tent
As Yisro, Moshe’s father-in-law, came to join the Jewish people, Moshe greeted him with a grand welcome. As the two reunited, we are presented with a vague verse. It says that “he” bowed to “him”. Rashi confirms the confusion by asking how can we know who bowed to whom? The answer is derived from the fact that the verse says, “one asked the other”, by using the word איש, literally man. This word teaches us that it was Moshe who did the bowing. How so? We see elsewhere that Moshe is referred to as “איש”, from the verse והאיש משה עניו מאד, Moshe was exceedingly humble. The Torah uses this word to hint to us that it was Moshe who bowed to Yisro.
However, this answer isn’t so clear. First of all, Moshe isn’t the only one referred to as “איש”. There’s a verse which refers to Yisro as “איש”: ויואל משה לשבת את האיש, “Moshe agreed to live with the Man”, meaning Yisro. Furthermore, why is the understanding of our verse derived from the verse describing Moshe’s humility? There’s an earlier verse which refers to Moshe as “איש”: כי זה משה האיש, “This Moshe, the man”. Why was a much later verse in the Chumash chosen?
The gemarra poses an interesting question. Part of the mitzvah to honor and revere one’s parents is to stand up in their presence. There’s also a mitzvah to stand up in the presence of one’s Torah teacher. What happens if someone’s son is their teacher? Is it appropriate for the father to stand up for their son? As well, is it appropriate for the son, the teacher, to stand up for their father? Essentially, the question boils down to which takes precedence: honoring parents or honoring Torah.
In this regard, Moshe and Yisro were on equal footing. Yisro was Moshe’s father-in-law, so Moshe was obligated to honor him. However, Moshe was the teacher of all of Israel, so Yisro was obligated to honor him. Since they were equal, this is what Rashi meant that we don’t know who bowed to whom. They were both obligated, but we don’t know who took the initiative.
To this, we are told that Moshe was called “איש”, as in the verse והאיש משה עניו מאד, that Moshe was exceedingly humble. This teaches us that due to his great humility, he forgave the honor due to him, and bowed to his father-in-law.
 Based on Shir Maon, written by the Chasam Sofer’s grandson Rav Shimon Sofer, brought in Toras Moshe I to Exodus 18:7. The Kesav Sofer ad. loc., the Shir Maon’s father, says similarly, although with more brevity
 Exodus loc. cit.
 Ad. loc., quoting Mechilta ad. loc.
 Numbers 12:3
 The Shir Maon cites this question from the Nachalas Yaakov ad. loc., probably because he is cited by Sifsei Chachamim ad. loc. However, this question is also asked by the Mizrachi, Gur Aryeh, Maskil L’Dovid, Be’er BaSadeh, Sefer HaZichron, and Ba’er Heitev ad. loc., as well as other commentaries. Mizrachi answers that this teaching holds that Ruel was Yisro’s father (and Ruel isn’t simply another name for Yisro), and it was to him that the verse was referring. We never find Yisro referred to as איש. Gur Aryeh says that in Yisro’s case it was normal to write איש, but it was seemingly superfluous by Moshe. See there where he gives a deeper insight into why Moshe is referred to as איש. Nachalas Yaakov and Maskil L’Dovid say the same. Be’er BaSadeh says if it was Yisro why is he referred to here as איש? It makes sense to say it was Moshe since not only is he called איש, but he was also humble (see note 12). Ba’er Heitev gives a few answers; see there
 Exodus 2:21
 Ibid 32:1
 I didn’t see any of the meforshei Rashi ask this question
 Kiddushin 33b
 The Rosh ad. loc. 1:56 points out that this question isn’t resolved. Since it’s an unresolved matter in a biblical mitzvah, we must be stringent, and both should stand up for each other. He then reports something interesting. As a result of this unresolved matter, the Rosh’s teacher, the Maharam MiRotenburg, from the time he accepted his Rabbinic post, never saw his father again. He didn’t want either of them to be confronted with this halachically problematic issue
 Shir Maon quotes the Tur and Shulchan Aruch Yoreh Deah 240:24, which rule that someone is obligated to honor their father-in-law. The source is from Dovid HaMelech, who referred to Shaul as his father (I Samuel 24:12). The Beis Yosef ad. loc. in Bedek HaBayis says this is also written in Orchos Chaim Hilchos Kibbud Av 5:1 s.v. ועד. The Bach ad. loc. says the source is really from Midrash Tehillim 7:4, which says מכאן שחייב אדם בכבוד חמיו ככבוד אביו. However, he’s bothered that other halachic decisors, such as the Rambam, don’t bring this halacha at all. He says it must be because of the dissenting opinion there which says that Dovid was referring to Avner, not Shaul (Torah Sheleimah ad. loc. § 41 cites the Hagahos HaGra who says there is no dispute). The Torah Temimah ad. loc. § 8 asks stronger, that seemingly there are better sources for this halacha, from how Moshe treated Yisro. Mechilta loc. cit. says מכאן אמרו שיהא האדם מוכן לכבוד חמיו. Yalkut Shimoni Yisro § 268 says מכאן אמרו שיהא אדם נוהג בכבוד חמיו. He doesn’t mention this, but Yalkut Shimoni is presumably quoting Mechilta D’Rashbi ad. loc. (which also mentions the source from Dovid HaMelech). If so, we don’t have an explanation for why the Rambam and others left this out, as this halacha is mentioned without any dissenting opinions. The Hagahos VeHearos on the Tur ad. loc. § 32 suggests that מוכן and נוהג don’t imply an obligation, unlike the source from Dovid HaMelech. As well, the Torah Sheleimah points out that Mechilta D’Rashbi disagrees with Midrash Tehillim, as it says נוהג, even with regards to Dovid HaMelech, unlike Midrash Tehillim which says חייב. Perhaps the Rambam ruled like the Mechilta D’Rashbi. However, the Hearos VeTikkunim by Rav Shlomo Buber on Midrash Tehillim ad. loc. cites Midrash Lekach Tov to Exodus 18:7 (as does the Torah Sheleimah), which says מיכן שחייב אדם להיות נוהג בחמיו כבוד, so that’s not a sufficient answer. Although, Torah Sheleimah infers from the usage of both חייב and נוהג that it’s not on the same level as honoring one’s parents. What’s interesting is the Aruch HaShulchan ad. loc. § 44 questions the whole source from Dovid HaMelech. We also see that Elisha called his teacher Eliyahu “father” (II Kings 2:11). We see that “father” is a term of respect which can be used to one’s teacher. Perhaps this is why Dovid called Shaul “father”, not because he was his father-in-law. He brings other examples. However, he suggests that since Shaul was trying to kill him, Dovid had no reason to honor him, if not for the fact that he was his father-in-law.
 The Mizrachi seems to say something similar: מי הוא הקרוי כאן איש הוי אומר זה משה שהוא ענו מאוד כדכתיב והאיש משה ענו מאד ומסתמא הוא היה השואל והמחתוה והנושק. Be’er BaSadeh also says somewhat similarly