My own view on dreaming in REM sleep is very opinionated! And I think there is a lot to be gained from actively reflecting on the contents of ones dreams. The article gives a clue as to why:

"How and why these emotions are reactivated is unclear. The prefrontal cortex integrates many of these emotions during wakefulness but appears paradoxically quiescent during REM sleep."

The prefrontal cortex is responsible for a lot of our "executive functioning"; the areas of our brain that work together to make decisions when we are awake. While we are awake both our emotional and executive functions are active, but in REM sleep our executive functions shut down and but our emotional functions do not.

What is so useful about this state is that it allows us to gain insight onto our underlying emotions without any concealment from our executive functions (which we often use to hide our emotional state from others while we are awake). If we focus on our own behaviour as characters within our own dreams, and less on the extreme circumstances we find ourselves in, we will surprisingly often witness ourselves perform odd behaviours, which, due to the nature of the quiet prefrontal cortex, are revealing of oddities in our emotional wiring. These disturbances within our emotions are what a good therapist is trying to find, yet our dreams can really do a lot of the diagnostic legwork (I believe it is their function).

A good example, which I include in a paper I wrote on the topic (https://psyarxiv.com/k6trz), was the dream of a friend of mine. She dreamt of a very dirty and smelly homeless man. In the room with this homeless man was a bed, but not a normal bed. This bed was dangerous and it would throw you into the air without warning. The homeless man told her he was feeling sad and he wanted her to come to bed with him (in a non sexual way). She did not want to fulfil his request, but felt she could not upset him and lay in the bed.

If you look at the situation (one the requires a clear but polite "no") and her response (a reluctant yes), and we layer on our knowledge that this is a purely emotional response, we gain a great deal of insight into how her unconscious emotional responses might be impacting her life (excessive responsibility for the emotions of others).

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It is also not surprising that the article finds that the dreaming brain has a bias towards unanxious interpretation of external stimuli. The brain is profoundly unanxious during REM sleep: the fight or flight neurotransmitter norepinephrine is ~80% below its base level during waking, and even though we might dream of scary things, paradoxically, our amygdala (the area of the brain responsible for threats) is as inactive as the prefrontal cortex.

There has been a great deal of research which compares dreaming to mind wandering. The level of stress that our brains are experiencing (norepinephrine levels + amygdala activation) dictate the contents of our mind wandering. If you fear flying and are sitting on an airplane before takeoff, your brain will be stressed and you will find terrible aviation outcomes popping into your head (the plane crashing on takeoff, etc.). These negative thoughts are designed to make you take avoidant action; getting off the plane!

However, as mentioned above, in dreaming our minds are distinctly unanxious. This, I believe, means that the brains design situations where we should be unavoidant. The dream with the homeless man is a good example of this. It is a great situation to say no in (it was notable that my friend did not feel physically threatened/coerced by the homeless man when she told me about the dream). These situations which urge unavoidant behaviour often provide a fantastic backdrop to contrast our purely emotional behaviour, which, more often than not, is disturbed by fears we picked up in our childhood.

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If you are interested in reading more please see my paper Dreaming Is the Inverse of Anxious Mind-Wandering, https://psyarxiv.com/k6trz.

It was discussed on HN here: https://news.ycombinator.com/item?id=19143590