Do note that it makes no difference whether there is combat involved or not, death evading is still a punishable rule violation, even if you do it in your own privacy while stunting or just generally freeroaming.
I still see it as death-evade because the person must either heal or get killed by someone else, also you have stated that he had enough time to heal so when he had done the same thing earlier when he was on low hp in Prawn-Island, would he still have enough time to heal?
I don't have any evidence about the past one he did, but seriously which fair player would kill himself if he already killed his opponent and he will still fight him after that. As I said he didn't do it only once but 3 times.. but still evidence is needed for that and I know. I will leave this for other admins.
Edit : As you can see in the video he was in a combat zone or close to a combat zone so he shouldn't have used the command /kill. He could have either escaped or fought.