I definitely like cool places where you can display your rank/prefix but for the kill messages, it would really be too long and would make the chat too cluttered. Maybe a place where this wouldn't be too bad would be at the start of the game when people are joining, the message could be like [Random] LukaG_ joined the game (12/16).
Otherwise, you can see the ranks in quite a few places. You see them in-game and in lobby chat, I often do /list or /online to see who I'm playing with and the ranks are there as well. Sadly Bedrock isn't Java, since you can also see it in the tab menu there. Otherwise, you do still have a fancy name colour to show off ;)
