This thread has gotten so offtopic away from Eldritch Knight / Valor Bard + Nick mastery, which isn't being discussed at all anymore.

Quote from Athanar90 >>

-"If you make a Light/Nick attack, there is never a point at which it is a Bonus Action attack. You simply get another attack with your Attack action." : While this is true, it misses the point. The attack made with the Light property is restricted in how it can be made and only exists within the context of the Light and Nick abilities, it cannot stand alone, meaning that anything that removes a qualifier that enables it removes the attack entirely.

I think my fundamental problem with this line of thinking is that every attack is "restricted in how it can be made"

Attack [Action]

When you take the Attack action, you can make one attack roll with a weapon or an Unarmed Strike.

Your choice of weapon then has further restrictions when it comes to things like range. You can't cast a spell though, or use a magic item like a ring of the ram.

Features/properties like Nick or Horde Breaker have additional restrictions, sure, but the whole point of War Magic or Valor bard's Extra Attack is to provide options above and beyond those restrictions. You get to tack 'or cast a cantrip with a casting time of 1 action' onto the end of the list of things you can do with an attack during the Attack action

Quote from AntonSirius >>

Quote from Athanar90 >>

-"If you make a Light/Nick attack, there is never a point at which it is a Bonus Action attack. You simply get another attack with your Attack action." : While this is true, it misses the point. The attack made with the Light property is restricted in how it can be made and only exists within the context of the Light and Nick abilities, it cannot stand alone, meaning that anything that removes a qualifier that enables it removes the attack entirely.

 

I think my fundamental problem with this line of thinking is that every attack is "restricted in how it can be made"

Attack [Action]

When you take the Attack action, you can make one attack roll with a weapon or an Unarmed Strike.

 

Your choice of weapon then has further restrictions when it comes to things like range. You can't cast a spell though, or use a magic item like a ring of the ram.

Features/properties like Nick or Horde Breaker have additional restrictions, sure, but the whole point of War Magic or Valor bard's Extra Attack is to provide options above and beyond those restrictions. You get to tack 'or cast a cantrip with a casting time of 1 action' onto the end of the list of things you can do with an attack during the Attack action

I like your line of thinking, but it really doesn't address my point: That, unless you're making the attack in exactly the way the ability states, you don't have the extra attack from that feature. There's other features that grant additional attacks that I would argue would apply to these abilities (such as the extra attack from Haste; it only limits the quantity of attacks, but is still an attack with the Attack action) but anything with restrictions above and beyond just being an extra attack exist only within their own context, not within the context of other abilities.

The order of operations in the way I'm reading it is essentially opposite the order you have. I'll use War Magic as my example, but both effectively work the same here. It effectively makes your Extra Attack feature read as follows:

You can [make two attack rolls with a weapon or an Unarmed Strike] instead of once whenever you take the Attack action on your turn. [You can replace one of the attacks with a casting of one of your Wizard cantrips that has a casting time of an action.]

Because this is an always-on ability, any additional conditions can still override it all, meaning that the Light+Nick and Horde Breaker restrictions being so specific disable any ways to use them that don't satisfy those conditions.

Quote from Plaguescarred >>

This thread has gotten so offtopic away from Eldritch Knight / Valor Bard + Nick mastery, which isn't being discussed at all anymore.

AntonSirius brought up Horde Breaker with Athanar90 as parallel mechanic to Nick and to contest the consistency of Athanar90's logic. Athanar90's position that the condition of the extra attacks from Nick, Cleave, and Horde Breaker has been at least internally consistent and can be defensible under RAW.

You joined in with activities not being part of the action that triggered them which has no rules basis. Your original argument that the follow up attack has to be made with a different Light weapon in order to exist has more merit and would carry over to Horde Breaker and Cleave. Nick, Horde Breaker, and Cleave are mechanically similar for the purposes of this discussion except Horde Breaker and Cleave are a little cleaner because Nick has the additional dispute of whether you have to attack with the Nick weapon first, last, or anytime.

The dispute is regarding this question 

When you can make the extra attack of the Light property as part of the Attack action instead of as a Bonus Action? 

Immediately when gain the ability to make this extra attack as a Bonus Action.

OR

When you make the extra attack. 

Quote from Athanar90 >>

I like your line of thinking, but it really doesn't address my point: That, unless you're making the attack in exactly the way the ability states, you don't have the extra attack from that feature.

Yeah, that's definitely the point at which our approaches branch off. To me, you either have an attack because you've met the conditions, or you don't -- and if you do, and it's during your Attack action, War Magic et al apply

I will say that narratively, the one I have the hardest time making that work for is Cleave, which seems clearly intended to be one single swing of your weapon that might connect with two creatures instead of one. It's hard to justify essentially replacing your follow-through with a cantrip

Light/Nick is an extra attack you get because you're wielding lighter, faster weapons, while Horde Breaker is an extra attack you get because you have special training against groups (cue Andre the Giant from Princess Bride). Narratively rather than mechanically, there should be no difference between them and a 'regular' attack

Quote from Plaguescarred >>

The dispute is regarding this question 

When you can make the extra attack of the Light property as part of the Attack action instead of as a Bonus Action? 

Immediately when gain the ability to make this extra attack as a Bonus Action.

OR

When you make the extra attack. 

 Well, that's one of the possible points of disagreement, but there's also, off the top of my head:

• What's the precise timing of replacement abilities?
• Is an attack with restrictions an attack for the purposes of a replacement ability?
• If you replace an attack with restrictions, do the restrictions apply to the replacement?
• What does that even mean?