When you have E-8s who are not in compliance with the regulations, is it OK to correct them on their appearance?

Making corrections if everyone's responsibility, regardless of what rank you are. As everyone else has said... It's all based off how you approach the situation. Be prepared to back up what you are correcting and do it away from everyone else and during down time. If that doesn't work... Work up your chain of command

Yes it is your responsibility to correct your superiors. Do it tactfully, but they are a reflection of your unit. If they are jacked up, then your unit is jacked up. I wouldn't do it publicly or in front of others. For example, I noticed one of my SNCOs had a long thread hanging from a spot on his uniform. So I asked to speak with him personally, I showed him there was something jacked up on his uniform, and he thanked me for looking out for him.

Just as they are looking out for you, it is your duty to look out for them. We each must hold ourselves to higher standards. But like I said, when superiors are involved, do it tactfully.

Being tactful I see no issue. I've corrected many soldiers in all ranks who still can't put their name tapes on right

Do it respectfully, pull them to the side out of ear shot of others. If that doesn't work tell your CSM.

I think we can stop asking "is it ok to correct (insert rank) when they are out of regs. Do it, will you bitten in the ass? Probably, but just do it and move on.

First off, BEFORE saying anything, are you 110% sure, look it up and note the reference (reg, section, paragraph and page). Second, you must be totally and absolutely "squared away" as well. Nothing on you is out of regulations, misplaced or in error.

Then and only then take the most senior of the group aside FROM EVERYONE and say
"I'm not sure, but something looks off and I didn't know if you knew it. Isn't (what is wrong) supposed to be (what is correct). If I'm wrong correct me. I don't know if you're testing me or not."

You give the option, then listen to the answer. Most will thank-you for being aware, a few might be "ticked" that someone so junior noticed.

Way back, there were many times that I, a mid-grade NCO had to correct a female junior officer on her dress and appearance (AFR 35-10) at the request of an other Officer (male). You need to "be the example" when doing something like this.

Please do, however, I highly recommend, just please ask him or her to speak freely and most important, make sure it's in privet, with no other ears around. You won't gain anything for your self or our Army, out of embarrassing anyone in public.

Corrections can be mad to whomever from whomever. But if you're going to make a correction:
1) you need to do your research and make sure you're right by regulation, SOP, policy letter, etc.
2) you need to be respectful and tactful when addressing them and their deficiency. Remember these are noncommissioned officers and despite whatever may be wrong with their appearance their rank deserves respect.
3) if they're great leaders and you're respectful and right by black and white print, they'll correct themselves.

Not everyone is an asshole leader, and for a ptv it takes some serious integrity to correct a MSG.

AR-670-1 is a DA mandate. Therfore it is entirely appropriate to correct anyone whether Enlisted, Warrant, or officer. Just remember to always display tact and respect for rank.

My opinion is to do it privately, being nonchalant about it, rather then corrective. The NCO knows the regs, corrective is not necessary and could become personally expensive. Treat him or her as any other solider as it is a matter of observation " boot lace is untied " " ranks upside down " etc. there is no judgement or corrective action, merely presenting a fact in a friendly manner. Never gave me an issue even with Full Birds. They are people too ;) You might be surprised you may get thanked.