Can Enlisted refer to Officers by their first name when off duty?

It's a bit different in the land of Guard and Reserves, Without getting into the legalities (because I'm not a lawyer and I don't want to spend 20 hours drafting a reply), when not in a duty status, we are essentially civilians. As such, absent the military context, yes it would be totally appropriate to refer to me as Vince if I worked for you, if we bumped into each other at (Civilian, non drill-weekend) church, or at the grocery store, etc.

I still address retired CSMs and the like by their rank or with Sir/Ma'am. Even if they told me to address them by their first name....I have difficulty. Even when in a operational environment where we have to use our first names....I still find it difficult.

I mean there are active duty who call each other by first name off duty. Hell I have been called by my first name by officers at work - but the majority were Air Force and they apparently call each other by first names. The last officer who did surprisingly was my last OIC...called me and the other two SFCs by our first name. It's weird after all this time...

No one cares what Reserve and Guard call each other when not at drill or on active status. I outrank my brother - he's Guard. I'm active. Both enlisted. The only time we were in uniform together was when we were deployed and I visited him and he came to see me to pin my stripes. After I got pinned I told him to drop...yeah he told me to f*off.

Now I'm a SFC he's a SGT. I was in uniform at his BLC graduation (I was stationed close to home on a compassionate and had to go straight from work) and I didn't expect him to call me Sergeant.

If I was in Reserve or Guard and worked with someone in my unit in a civilian job I would definitely not be a dick about rank when we aren't at drill or active.