Yes. Fragging can kill a coral. If done incorrectly the coral could get an infection, and die pretty quickly. That is why most wil immediately dip their corals after fragging to decrease the likelihood of the coral getting an infection from essentially being cut in two. Or more.
Even then, dipping would only lessen the chance of infection, and a very sensitive coral could still wind up getting an infection and dying anyway.
What type of coral was it?
It was a golden torch, and he fragged it in water. I doubt he dipped it after as it’s attached. I noticed yesterday some sliminess (?) from I’m assuming the two branches or so he had fragged
So the conversation went something like:
H: Oh no! ;Jawdrop My golden torch died.
M: What?!? ;Wideyed..........(in shock) Did you kill it?
H: What??? :mad: Why would I do that? Stop being ridiculous.
(After a few minutes of sitting in silence)
M: ;Shy I don’t think my mopping killed it.
H: I’m not mad at you. We already fought about this yesterday. It was fine yesterday.;Sour
M: But it wasn’t actually looking very healthy. I think it was doing poorly. Looking at this picture from a month ago and then this one from yesterday ;Sorry (yes, I took pictures just in case)
H: That’s because I recently fragged it out to a friend. ;Bored
M: ;Meh Are you sure that’s not what really did it? That could have been traumatic. It wasn’t looking happy and was probably already dying. It just so happened to die last night. ;Shy
H: ;Rage You don’t know anything. Stop being so stubborn and admit this is one area that I know much more than you.
M: I’m just saying it could have been the fragging. I doubt it died from mopping.
H: ;Punch You don’t know what you’re talking about! I’m an expert at fragging and know what I’m doing. It has nothing to do with that! I only cut off the branching pieces. It was healthy and fine. Coral fragging is actually good for propagation. (...then some fish lingo I didn’t understand).
M: But look, all your other corals are fine! The same one in this other tank.

H: That’s because last time you mopped I did a water change and carbon filtration. I don’t usually run that stuff because it’s expensive to maintain (...coral jargon). I should have done it for this tank but I was so mad at you yesterday.
M: But it didn’t die in the other tank yesterday...
...........
...........
M: I didn’t kill your coral from mopping...;Shy
A few minutes later:
M: I’m sorry I killed your coral. ;Sorry
H: I wasn’t mad at you, but now I am upset at our conversation and what you insinuated. I need to go clear my head. ;Shifty
Saltwater aquariums create so much drama and stress in my life. I still think it’s perhaps the fragging that really killed it. It’s all just bad timing and poor luck. Nothing else died. Literally the same other coral in a smaller tank in the same room. I’ve also talked to a few other people (wives mostly), and you all, of course. They’ve said they use all kinds of chemicals, even bleach on floors with no issues, so I dunno. I use nothing else in my house because he’s so insistent. Vinegar and baking soda are my best friend but sometimes just not enough. Really, like this is the only time. I go nowhere near his tanks because he’s such a purist.
Anyway, it’s always hard to admit you’re wrong. I honestly feel there were other factors at play, but there’s no way to tell. Wish corals and fish could talk or something. Like, “Hey coral, did it bother you when I mopped yesterday? Why do you think your posh friend over there died? You feeling okay today, fish?” ;Hilarious
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