Should a 2LT salute a 1LT?

A 1LT outranks a 2LT, thus the 2LT will render a hand salute (right hand) and the proper greeting
of the day: (Good morning, Sir, Good afternoon, Sir, Good evening, Sir and Good night, Sir. The 2LT will hold his salute until the 1LT returns the salute. Give a crisp salute that Snaps with the proper
greeting AND THIS IS HOW YOU WILL BE REMEMBERED, especially by an officer from your unit.
Give a sloppy salute and garbled greeting (perhaps because your mouth is full of chewing gum, etc)
and THAT ALSO WILL BE HOW YOU ARE REMEMBERED! And remember even Generals & Admirals have to salute a Flag Officer higher in rank than themselves.
Exceptions. If you are in a combat area where you may be observed, it might be SAFER not to salute.
Snipers take fiendish delights in shooting officers and RTOs with their antennas sticking up and
waving around.

In civilian life, we say good morning, afternoon, or evening so I think it is no different between officers especially if they expect such curtsey to be offered to them. As far as saluting, the issue is less visible amongst enlisted since salutations are verbal but another sense, I also see it in the direction of a SSG who would not stand at parade rest while talking to a 1SG but expect soldiers below them to offer such respect.

And, in keeping with LTC Shewbert's comment about Non-coms. If that is a common attitude, those Non-coms need to reflect on the following: If they are enlisted leaders as E-5 thru 9, do they not realize that the E-1's thru 4 look to them for guidance, but just as importantly those EM will model their superior's behavior (just like little boys mimicking their Dads). Is that was these so-called experienced Non-coms think? They are responsible for passing on time-honored military traditions and protocols to their subordinates. As a former E-5, W-2, and O-3, I ALWAYS saluted those who held a higher rank. It was not an onerous obligation. It was a privilege, and done out of pride. One of the first things that General Patton did in inheriting a demoralized army in North Africa after the disaster at the Kasserine Pass was to insist on military courtesy. After some initial resistance and even puzzlement, the soldiers eventually became known for their spirit and professionalism in the "Patton salute."

Out of respect for the rank, yes a 2nd LT should salute a 1st LT.

An old saying in the Corps states "seniority among Lieutenants is like honor among whores, there ain't any"!

I say yes. Just like a LTC should salute a Col. Or a Brig Gen should salute a Maj Gen....etc

I don't think it's necessary for single bars (W1-W5 and O1 and O2) to salute each other when it comes to just passing each other on the sidewalk.

I was 18 when I went in. I got out three years later. I learned respect for rank, position, and the Army way. If a CSM, 1SGT, or even SFC have to salute then a butter bar should as well. Respect starts with the uniform. It is then the rank then person. A butter bar has to learn just like a pv1. If a pv1 can be put in parade rest by a PFC or Specialist then a 1LT has to learn (some need as much reminding as possible). I work with a ret. 1sgt and I still refer to him as top (as I did in the service).

When I was a 2LT (1967) we never saluted 1LT's. When I was 1LT we did not expect 2LT's to salute us. We considered LT's the same. We did salute Captains as they generally had more time in service & certainly more experience than LT's.

Guess I am old school when it comes to customs and courtesies. You respect the rank and not the individual. Salute an officer who out ranks you whether you are a 2lt etc.