[quote=@LunarStandard]
<Snipped quote by Xeiyenreisha>

Okay, time to put on my lawyer glasses and clear up some rulings.

Light and Darkness Dragon only negates the activation of the Spell and Trap cards themselves. If a Spell or Trap that is already face-up on the field activates its effect, LADD cannot negate that activation, as it was the activation of the effect, and not the Spell or Trap card itself. It's perfect legal to negate Lightsworn monster effects though, although due to the rapid-fire nature of their milling effects, that ATK will be dropping awfully quickly.
[/quote]

Light and Darkness Dragon effect:

Cannot be Special Summoned. While face-up on the field, this card is also DARK-Attribute. Once per Chain, during either player's turn, when a Spell Card, Trap Card, or monster effect is activated: This card loses exactly 500 ATK and DEF and that activation is negated. When this card is destroyed and sent to the Graveyard: Target 1 monster in your Graveyard (if possible); destroy all cards you control, also Special Summon that monster (if any).