Just for clarification, do we know if the Corporal Palmer we see in Palace Hotel of Evolutions is the same Palmer in 4 and Guardians?
No they are different. Here’s Corporal Palmer’s Halopedia article, which is different than the Commander Palmer article. Palace Hotel isn’t fully canon though since it’s events take place at the same time as a couple levels in Halo 2.
I have wondered that for some time. Cpl. Palmer’s tone does remind me of Cmdr. Palmer’s though, regardless.