The bolded is what inspired me to make this thread. It seems like people like this don't want anyone to be happy if they aren't happy, but I question if that's what's really going on? Like perhaps they're just defending and protecting their belief system that brings them comfort instead, which has the side effect of making others miserable. Maybe it's not deliberate.
When I feel miserable, seeing happy people heightens my misery because it reminds me of the things missing from my life that put me in a state of misery to begin with.
When I am miserable, I don't want to make others feel the same, but I also have a tendency to want to talk about it which can leave me feeling a bit conflicted as to how much of my misery experience to share. I also want to find others that already feel that way (or have felt that way) so I feel less alone in my misery - there is comfort in knowing that others are or have gone through what you are going through. I don't know if I would say that people that feel this way "enjoy being miserable", but its more that they have accepted it as a part of themselves and as a part of life and part of being alive (when you have felt the depths of misery, then you also can have greater appreciation of joy and happiness through knowing the contrast and the phrase "I'd rather feel pain than feel nothing" may also apply in the case of emotional misery) and they may try to express their oneness with misery through some form of art such as music or poetry (this seems fairly common in gothic music and poetry).
As you mention, there are those that want to inflict their misery on others, but I don't think those people actually enjoy being miserable, but they may enjoy bringing other people down. I think anger and bitterness are the factors at work there, and doing so may make them feel good (I can understand it
if they actually blame that person for their misery, but when its a third party, I think its a case of lashing out at those that they can because they feel powerless regarding the source of their misery - they may or may not want others to share their misery, but more often than not (in my observations, but it also depends on how unhealthy the person doing it is) they are simply having a natural lack of self control due to stress and are "not themselves"). A person doing that could just be a highly stressed individual, or they could be a bitter sadistic person, but in either case, unless they are also a masochist, I highly doubt they enjoy misery (or even have reached a point of misery acceptance as described above).
That is different than those that want to share/express their misery either as a form of expression or as a way of crying out for help and support.
There is another category that I forgot to address initially as well. There are those that feel they deserve it, so they embrace it as a form of penance for their perceived wrongs. I don't think such persons would want to bring others down to their level of misery, but they want to show they are suffering so others see them as repenting.