Players can prevent fire damage by reloading world/re-joining server

When you're on fire, you can reload your singleplayer world or re-join the server to prevent taking any damage from fire for a couple of seconds. By constantly reloading the world/re-joining the server, you can end up getting no fire damage from a fire source, because the fire damage timer that determines how long you're on fire still plays while being invulnerable.

This is probably due to invulnerability frames after re-entering a world/server, but as this mechanic can easily be exploited, I believe this is unintended behaviour; as a comparison, the "no fall damage" exploit still exists in singleplayer by reloading your world, and the report is not marked as WAI.