Basically, when you combat tag someone, you are able to use an elytra by spamming space bar, which allows you to fly on your end, but the server and other players will recognize you as standing straight up, when you are really flying. This can be used to replicate increased speed, flying, and other stuff, and it could potentially be abused by some people during fights. Be warned, if you try the glitch, eventually it will ban you, but not right away.
You can also "fly" by spamming spacebar and it seems to be more effective than normal flight at keeping in the air over a long distance. I would suggest switching to a broken elytra while saving the data/lore to completely disable flight.