How many NCOs get sick when they hear Soldiers referring to each other by first names and hear other NCOs doing it or allowing it.

Went thru that and played it out like I had no idea who they were talking about! Then stated clearly oh YOU mean private Jody? Using there last name and rank! did that with the officers to. Wasn't long and didn't hear first names anymore. They got the hint that wasn't professional and I wouldn't deal with their lax attention to detail.

I never allowed it while during duty hours when I was in. It was either by rank or last name or both depending on situation. If someone including officers called me by first name I ignored them until they called me by rank and/or last name. Off duty out on the town with my friends was the only time I would allow and then we usually had nicknames for each other anyway. The only exception was spouses, girlfriends of soldiers or other civilians

It depends on your line of work. I think for cultural assimilation and security in small teams, first name basis may be used. You tend to get more information from a KLE when you are relaxed and comfortable.
Most of the Cadre at SWCS refer to themselves (when speaking casually amongst themselves.. Never to us) by first name. All of us on my team, and most in the class refer to ourselves by first name unless situation dictates otherwise (high vis area).

MSG Sommer Brown I agree with you. It irritates me to no end. I believe it leads to a breakdown in structure. When people lose their military bearing, they get too comfortable and lax in their behavior and even try to "negotiate" their way about doing things. Orders become more like suggestions and then we have to get in to a "discussion" about reminding them that they're actually in the military and orders are not up for negotiation or discussion.

The best thing is to have the leadership help enforce the respect that is to be given to whatever service insignia you wear and for everyone to address each-other appropriately.

I do not use first names because most people do not go by them in military. I have attempted several times during my short career to locate anything on paper that says that the Last Name is the only or proper name to use. I have been very unsuccessful. I would prefer to hear my first name more often, when I worked before the Army I spoke to people using their first names unless asked otherwise. Seeing how this is a subject on personal courtesy and personal pet peeves I guess you play the military games and try not to upset your superiors when they are around. I personally don't like unwritten rules, so for me I have no issue with people using my first name or others until I see something on paper.

I cannot speak for the other services, but as a Soldier, this drives me absolutely ape sh*$ crazy. I've been a part of the active duty world and the Reserve world and been witness to the Guard world. In the active duty, it seems to be officer led and driven, and some senior NCOs that I have heard. It's a lot more common in the Reserves and Guard, and even more common if unit members work together in civilian positions. If you work with someone Monday through Friday and call them by their first name, remembering 2 days a month to call someone by thier rank or last name might seem difficult. To me, it speaks to your professionalism.
I've worked at my last several military assignments with lots of civilians, either contractors or DoD types; and correct them a lot of they send me an email addressed to Jerilyn (my first name). I am not here assigned as a civilian, I am a military member of this community, please address me by my rank, SFC, my last name, McConchie; or if you can't pronouce or spell that, SFC Mac. It's pretty simple and easy.
My family are the only ones entitled to call me by my first name! I would want my family members to call me SFC Mac. It's, again, a matter of professionalism. Are you sloppy? "Hey Joe, let's go to the motor pool." Or are you a Soldier? "Hey SPC Blaze, can I catch a ride with you to the motor pool?"

Depends on the situation. In public, I always use full rank followed by last name. In private (eg counseling sessions, giving career advice), I will use first name ONLY if I think it will put the Soldier at ease. I want him/her to hear and absorb what I'm saying at the personal level and don't want rank standing in the way.

Ask any of my past or present Soldiers, and they'll confirm I operate this way, and it works.

As long as it is kept professional in the work place, I don't see the problem with it. I was enlisted, my best friend is an O-4. At no point, did I ever refer to him by his first name whenever I had to deal with him in a working situation. However, on weekends, in one another's garages, it was always first names.

If there are two people of the same rank doing it and it's not for work, I don't worry about it all that much.

If it's becoming the SOP for how they interact, THEN I step in and ensure that they maintain a professional bearing while on duty.

But I don't worry about "ever hearing it", because that's just too far down the crazy hole.

Being in the reserves I have a skewed opinion on this. Most of the guys that I serve with I am very good friends with outside of the Marine Corps and spend more time together in that aspect than in uniform. That being said, we do try and refrain from it while in uniform but if we are in a group and it just us we routinely call each other by our first names. When lower or higher enlisted are around, we generally go back to Rank Last Name.