If a fighter grappled another fighter, it seems to me that both should lose any benefit of dexterity to armor class when attacking each other within the grapple.
A grappled character could have disadvantage against the grappler using any weapon that requires a good swing, but if the grappled character used a dagger--I imagine the grappler would be in grave danger--advantage at the least.
The D&D 5e rules leave this up to DM ruling it as far as I know. What is the most consistent way to rule attacks in the context of grappling which makes sense and doesn't allow grappling to be an absurd buff which breaks all the familiar-world rules of martial contests?
Part of what I am asking is how other Dungeon Masters apply advantage or disadvantage in a grappled situation between two humanoids