Jhanic concentration and feeling

I believe you can directly look into thought when you develop abhiññā. But at a lesser level meditation increases your ability sense the moods and emotions of people around you (spiritual awareness). This can happen though vipassana also as you stay contemplating internally and externally.

4 Modes of Mind reading as per Sampasadanīya Sutta:

Mind-reading Furthermore, bhante, unsurpassable is the Dharma that the Blessed One teaches concerning mind-reading. Bhante, there are these four modes of mind-reading:

(1) Here, bhante, by means of a sign, one declares: ‘Thus is your mind: this is in your mind; such is your thought.’ And however many such declarations he makes, they are exactly so, not otherwise. This is the first mode of mind-reading.

(2) Furthermore, bhante, one does not make his declarations by means of a sign, but after listening to the sounds of humans, of non-humans, or of devas, having heard their sounds, one declares, ‘Thus is your mind: this is in your mind; such is your thought.’ And however many such declarations he makes, they are exactly so, not otherwise. This is the second mode of mind-reading.

(3) Furthermore, bhante, one does not make his declarations by means of a sign, nor after having heard voices of humans, of non-humans, or of devas, but from having initially applied and sustained his mind, listening to the sound of a person’s thought-vibrations, one declares, ‘Thus is your mind: this is in your mind; such is your thought.’ And however many such declarations he makes, they are exactly so, not otherwise. This is the third mode of mind-reading.

(4) Furthermore, bhante, one does not make his declarations by means of a sign, nor after heard voices of humans, of non-humans, or of devas, nor by listening to the sound of a person’s thought-vibrations, nor from having initially applied and sustained his mind, and listening to the sound of a person’s thought-vibrations, but by a samadhi free from initial application and sustained application, one knows the mind of another with his own, thus: ‘By the way the mental formations of this good man are inclined, the depth of that mind will think such and such a thought.’ And however many such declarations he makes, they are exactly so, not otherwise. This is the fourth mode of mind-reading. With regards to mind-reading, bhante, this is unsurpassable.

Yes, people who become deeply quiesent and stable do aquire such abiility. I'm no expert, but have seen it in action and have discussed with one person who was very profoundly skilled. You just "know". Specific mode of perception (knowing) is highly individual. Some get visual images. It is akin to when you "know" something by direct experience vs "think so".... it seems one can bypass the direct experience part and arrive at "know" without it. If you have ever known a skilled clarvoyant its less of a stretch to accommodate this fact. Its well known and refered to in samatha teaching settings. It is said to be important to not get too occupied by this, it is a distraction (maybe the booby prize) from more important goals. I think its a by product of quiescence and stability. If it is your goal ... that will be an obstacle. The very strong source I'm heard refer to this is Alan Wallace, super brilliant, a guy who has tremendous training and experience.

It is inappropriate to ask such questions, because they unequivocally end in an argument which is basically the same as trying to convince someone in the 14th century of how an aeroplane works. It simply isn't possible to explain without the experience.

Imagine trying to describe the colour blue to someone who has not seen it.