These Ruling(s) have not been confirmed as applicable to the TCG.[Notes 1]
Herald of Orange Light can negate any monster effect activated by your opponent. ... "your opponent controls" is referring to "effect" not "an Effect Monster". The card still cannot be used to negate your own monster effects.
These TCG rulings were issued by Upper Deck Entertainment and have since been deemed unofficial by Konami. They were previously considered official and can still be correct, as long as they follow the official gameplay rules, or unless Konami has issued a ruling that says otherwise. References: 
If an attacking Effect Monster or an Effect Monster that is being attacked activates an effect during the Damage Step before damage calculation, when "Herald of Orange Light's" effect is chained to negate the effect and destroy the monster, damage calculation is not performed. Also, a replay does not occur.
↑Email Rulings are considered unverified, as their source(s) are not publicly viewable. They are not confirmed as applicable to the TCG until they have been officially published by Konami.