Quote from Plaguescarred >>

I realise this POV is in minority, but i'll try explain it in different way.

You make a D20 Test with the corresonding ability and add the modifier delireved from it. You don't make a D20 Test with more than and it's the modifier derived from the score of the ability that you add,

Ability Score and Modifier: Add the modifier when you make a D20 Test with the corresponding ability or when a rule asks you to do so. See also chapter 1 (“The Six Abilities”).

 You forgot about "Circumstantial Bonuses and Penalties". 

Quote from Plaguescarred >>

I realise this POV is in minority, but i'll try explain it in different way.

You make a D20 Test with the corresonding ability and add the modifier delireved from it. You don't make a D20 Test with more than and it's the modifier derived from the score of the ability that you add,

Ability Score and Modifier: Add the modifier when you make a D20 Test with the corresponding ability or when a rule asks you to do so. See also chapter 1 (“The Six Abilities”).

 I truly empathize with your point of view and understand the arguments, but still, that rule refers to a D20 Test, not to how the damage is calculated:

Damage Roll

A damage roll is a die roll, adjusted by any applicable modifiers, that deals damage to a target. See also chapter 1 (“Damage and Healing”).

EDIT: if it's relevant, in this text from the Rules Glossary, and the one I previously quoted from the Damage and Healing section, "modifiers" is used in plural.

I found this conversation on sageadvice.eu. After reading it, I understand this means is valid to apply the same modifier twice: from your spell casting ability modifier (WIS) + Potent Spellcasting (WIS again).

@danthebran Does the Arcana Cleric's Potent Spellcasting add +WIS mod damage to the 1st target of Green-Flame Blade, the 2nd, or both?
@JeremyECrawford Potent Spellcasting adds to dmg. dealt by a cantrip. GFB: add to 2nd target, then to both targets at 5th lvl.

TarodNet Good find, Potent Spellcasting had similar verbiage which was intended at least at the time to add ability modifier multiple times so let me side with you on that.

Quote from Plaguescarred >>

TarodNet Good find, Potent Spellcasting had similar verbiage which was intended at least at the time to add ability modifier multiple times so let me side with you on that.

 Sure thing, adventurer!

To be honest, when I created this thread, it was because I had that big doubt. I'm glad everyone agrees with these kinds of interactions.

In the 2024 PHB, situations where the same modifier can be applied to calculate damage are relatively easy to get, which I think weren't as common in the 2014 rules so I was lucky to find those tweets yesterday.

Thanks Plague!