This question emerges often in the present times, because we live under the continuous brainwashing regime of nihilism and we are led astray by the hammering propaganda machine of nihilist secularism. Nihilism itself being evil, it wants to make us forget the truth that has been common sense for millennia.
We need therefore to refocus our reflection on this subject by first freeing ourselves from the chains of nihilist prejudice, because if we no longer know what a positive value is, we cannot know how and when it could be lost.
Let's listen to the teaching of someone living in a (quasi) nihilism-free time: we find a meaningful quotation in Dante's Convivio (part IV, chapter VII):
"...is dead and walks the earth...is dead and looks alive...truly dead the evil man can be said..."
[ DANTE ALIGHIERI, Convivio, IV, cap VII
"Ultimamente, quando si dice: E tocca a tal, ch'è morto e va per terra, a maggiore detrimento dico questo cotale vilissimo essere morto, parendo vivo. Onde è da sapere che veramente morto lo malvagio uomo dire si puote, e massimamente quelli che da la via del buono suo antecessore si parte."
http://www.greatdante.net/texts/convivio/convivio.html ]
Although his thought can be described in ethical terms too, the sentence that Dante proposes to us expresses a knowledge, not a wish nor a metaphor, it states a fact. The evil man is a dead man walking on earth.
Why does Dante say that ?
In that passage Dante is speaking about those who had great predecessors whose piety they don't follow nor repeat, and instead they stray.
This can help us to understand: we can say that all forms of teaching are all around us, they come from many sources and in many forms ... And thanks to all the teachings, thanks to the Sacred Tradition, we can grow, because, among many other Gifts, we have received the Gift to be able to learn (to hear and see) the Truth. That Gift allows us to grow to our full humanity.
But we need to have THE WILL TO LEARN if we want to grow to the full blooming of our human potential.
Can a human being choose to do evil and still have the Gift to be able to learn(to see and hear the Truth) ?
This is how the question "Is evil "not punished" indeed ?" must be framed in non-nihilistic terms.
The evil person chooses to reject the Gift (the ability to learn - to see and hear the Truth) because the evil person chooses to reject ALL and every Teaching and to make of himself/herself the sole center of reality... and in so doing chooses to live as a not human.
Learning to see and hear the Truth actually means living out of ourselves (ECSTASY: EK out, HISTANAI to stand). (And someone will want to add : reaching the Goal [which of course is a paradoxical expression] of Seeing and Hearing means RETURNING to ourselves, changed forever, to a paradoxical "ourselves").
"Ecstasy" is the Wonder in front of the miracle of the Eternal Creation, the Awe in front of the Infinite Beauty that mirrors the Infinite Love of God, the Joy in front of the unfathomable Mystery.
Live ecstatically ...
How do you feel when you listen to the song of the Queen of the Night in Mozart's Magic Flute ?
Can you hear the reflection, the - immensely far, and yet mysteriously near - echo of the Original Sacred Word that creates the world ?
How do you feel when you contemplate the Holy Trinity (The Angels at Mamre, Genesis 18: 4-8) by Saint Andrej Rublev ? Can you see/feel the Kingdom of the Spirit looking at you through the window of the icon ?
Let's remember here the wonderful paradox written by Pavel Florenskij (in his essay "The icon"):
"Of all the philosophical proofs of the existence of God, the syllogism "The Trinity by Rublev exists, therefore God exists" sounds as the most persuasive."
Even if you don't know what Florenskij is talking about, you feel a mysterious presentiment that you could in fact understand it very clearly, don't you ? Presumably yes, because one part of the spirit of every NOT evil person lives ecstatically (even when we don't want to be aware of this dimension of our life)
Rejecting the Gift means attaining the contrary of the Vision, of any trace of the Vision.
For the evil-doer, the world and life itself turn into a meaningless, solid, nothing. A despair-moved, grabbing-grasping, hell.
Easy to detect, by the way, in the radical inability to smile.
Matter of opinion ? Not at all.
Rather, this terrifying SELF punishment of evil comes in such a way so as not to disrupt nor hinder our other great Gift: Freedom of Choice. It comes SUBTLY. (Except for the evil-doer of course, whose devilish sardonic posture cannot cancel a iota of his granitic despair. But this is not visible to the world.)
Exactly as it happens with the Miracles in positive, that come hidden to the world, and are only visible " out of the corner of your eye".