Can soldiers in civilian clothes salute a fallen comrade memorial?

Under normal circumstances, a salute is a show of respect to the officer corps.

As a veteran, I render a salute to my fallen brothers in arms out of respect to their sacrifice.

Remember Freedom isn't Free!

Absolutely, we all served and have that moral right with or without anyone else's approval. The older I get, the more important these things have become.

Try and stop me.

Short answer: Yes.

Longer answer: Unless something is prohibited by law, regulation, or orders, it is permitted. The US Flag Code (Title 4 Section 1 USC, for those who want to look it up) makes no mention of when it's impermissible to salute the flag (pro-tip - it's always permissible, unless you're in formation or other condition that expressly forbids it). I'm also not aware of anything that prohibits saluting memorials, graves, etc. So if you want to do it, you're fine. If someone tells you you're wrong, thank them for letting you know, and ask them (politely and gently, so it doesn't sound like you're saying, "Oh yeah? Says who?") if they can tell you what law, regulation, or order prohibits it. If they don't know, feel free to go back to doing it when they aren't around (doing it when they are is unnecessarily antagonistic, and since you aren't required to do it, our fallen comrades will understand if you miss it once or twice to keep the peace with a living comrade).

Alternatively, if there's a US flag at the memorial (which I'm sure there is), salute *it* out of respect for those memorialized.

Just let them try and stop me from doing so. As they will be opening a can of worms they dont want to open.
Even when they presented me with my dad's casket flag at his funeral in 1999, I stood up and returned the salute I received. Je was a combat vet, two wars, he was my father and mentor, and he was a brother in arms. He brought me up to Honor the Flag, Honor our Military, and Honor our/my fellow Veterans.

Saluting in most instances is a customary act. Saluting the grave of a fallen friend is certainly appropriate even if it isn’t spelled out. Btw as a matter of custom and regulations Marines never salute uncovered.

I have done it at the tomb of the unknown soldier. Just out of pure respect for those that came before me. I will never fault any veteran who offers respect to their brothers and sisters.

I am all for saluting a fallen comrade. The love and respect in that gesture was earned by the fallen.

The survey results speak for themselves.

Of course!