Half the time my lunge carries me through my enemy causing me to miss entirely, or causes back smacks to be regular hits, as I phase through the "back" hitbox into the front hitbox.
If other players were solid objects in the world, melee would feel tight and exciting. As is hitting the melee button early to avoid "lunge through" causes a bunch of lost melee punch-outs which makes it less fun.
There's also the issue of friendly Spartans phasing through me mid gunfight and interrupting what was otherwise a tense moment of "who will win?"
More often than not an ally will block my shots, while missing my enemy entirely, and allowing them to just run away totally ruining a kill, or inadvertently saving me and not giving me the satisfaction of finishing a gunfight win or lose.
Please 343 just give us player collision. It creates more interesting gameplay moments and prevents melee from being a guessing game.