It is a Dodge Reaction. - Before the final version of the Conan 2d20 rules, anyone could decide whether to make a Parry Reaction (using the Parry skill) or a Dodge Reaction versus a Melee attack.
After the changes, you could only Dodge Ranged Weapons attacks, and only Parry Melee attacks.
The Parry Talent “Reflexive Block” allows you to use a Parry Reaction versus Ranged Weapons attacks.
The Acrobatics Talent “Pantherish Twist” allows you to use a Dodge Reaction versus Melee attacks.
Pantherish Twist is NOT a Skill substitution Talent!
Pantherish Twist allows you to make a different type of action, a Dodge Reaction, versus a Melee attack, which is normally not possible.
But the Skill for a Dodge Reaction remains the same - Acrobatics.
So all Acrobatics Talents apply as for any other Dodge Reaction.
Apparently, I was too much under the impression of the first 2d20 RPGs, Mutant Chronicles, where you do have a Dodge and a Parry Reaction.
In Conan you only have a Defend Reaction.
And the way Pantherish Twist is worded it does look like a Skill substitution Talent, that allows you to use the Defend Reaction, but substituting the Acrobatics Skill TN and Focus for the Parry Skill.
And so the nature of the test is still a Parry test, which means all the Parry Talents apply (like Deflection, Riposte).
I find it often very interesting how things are very different in the details between several 2d20 RPGs.
In my games, I assumed the Pantherish Twist to grant the “usual” Dodge Reaction, and therefore be an Acrobatics Skill test.
But due to your question and re-reading the description with a fresh view-point, it is worded exactly like other Skill substitution Talents.
So I have used it WRONG all the years in granting the re-roll for the Agile Talent, but not granting the application of Deflection or Riposte on a Defense Reaction using Acrobatics.
But now, as it is clearly a Parry test, which uses Skill substitution, no re-roll would be applicable, but a Riposte is now perfectly fine.
There is one thing unclear now: Pantherish Twist allows you to generate 1 Doom less on a Reaction using the Acrobatics Skill.
The Parry Talent “Deflection” allows the same for a Reaction using the Parry Skill, which in the case of Pantherish Twist gets substituted by Acrobatics TN and Focus.
That would mean, Pantherish Twist plus Deflection plus a weapon with the Parrying quality would reduce the Doom generated for a Defense Reaction by 3 points. - That’s a lot.