Should a 2LT salute a 1LT?

Yes! They are not the same. A brigadier general salutes a major general. They are both generals, but all are different O grades.

Absolutely, always salute a superior. My father, who served prior to WW2 as enlisted and then WW2 and Korea as an officer, taught me "When in doubt, salute. It's better to be wrong than disrespectful."

Let's break this down,
first and foremost, we need to distinguish seniority.
Within our military application, we find several variations within the rank structure,
a Warrant Officer has an Identifying component of
W-1, W-2, W-3, W-4, and W-5 each holds it's own ranking level,
just as a Lieutenant, the identifying component changes formats
with a 2nd Lieutenant being of a lower rank to the 1st Lieutenant,

So with that said, we first and foremost should always return to the proper military etiquette, by simply addressing each of the military ranks by a formal address, We do not salute simply in an exchange of honor, we salute as a privileged gesture of respect and trust among soldiers, Just as when we address Enlisted ranks from Private to junior Nco's and Nco's each is applied by a designated identifier which shows commitment, abilities, and professionalism when addressing personnel.

The regs say it all! When I was on active duty and I seen people not doing what the Regs said I would walk up to them and would salute them and would ask them if they understood what is required of them.

A salute is a recognition of Service Member/Warrior to Service Member/Warrior. It's a gesture of respect and trust. Whether we salute each other perceiving a place of 'power' or 'obedience' that's your story and Ego. Preferably (IMO) it's a mutual recognition; I honor the light and strength within you my Brother/Sister in Arms; 'Namaste" or "Sat Nam" ... I SEE (RESPECT) YOU." We salute in recognition of our shared mission to make the ultimate sacrifice (of self is easy...family and community; greater).

Absolutely yes

*blink* Um, yes . . . At the very least that butterbar survived to get promoted and didn't end up as chow for a MSgt somewhere . . .

I can see that, quite clearly, half the universe on here has chimed on about this one here...that being said, wherever I was, or had to go, it was always done, as well as insisted on, plus, I always did, purely as a matter of habit and conditioned reflex, end of story, guys, honest....

The phrase we learned early on in the sixties was "Honor among lieutenants is like virtue among prostitutes." Perhaps the fact that we were only 2nd Lieutenants for one year and a captain by year three created the notion that there was no need to salute a First Lieutenant. Add to that that the overwhelming majority of us were two-years-and-out officers.

Most of us were First Lieutenants upon arriving in Vietnam, in fact, I have a hard time recalling meeting any 2nd Lieutenants during that year. By the time I left in August of 69 Lieutenants were often not saluting Captains, especially if the Captain had been promoted toward the end of his tour.

This is about the time that the field army was beginning to suffer. Troops were refusing to salute any officer, let alone a Lieutenant. Stories of fragging began to become more frequent, Article 15s were becoming a burden on the administrative sections and court martials increased notably.

Simple YES
O1 is junior in grade.