I wouldn't say "revel" is the right word but I do like it. For example I only really want to listen to music where the artist is expressing their pain. And it hurts me if I find out that really they are happy. I think it is from the loneliness of pain. We want to feel like we're not alone and so someone expressing something we have felt too is a comfort. If it turns out they have experiences we can't access like happiness we feel abandoned, and more alone. That's a little bit different from jealousy. I definitely don't feel this way when I am not actively depressed, because at those times I can recognise that everyone's experience has a mix of both suffering and happiness. But when I'm depressed I don't believe in happiness, I only believe in suffering. Seeing someone else express happiness is therefore extremely jarring.
If someone in real life came up to me and expressed out loud all the details of their suffering, I wouldn't enjoy that and would find it painful, I would have empathy for them, I would feel their pain. I suppose it might slightly alleviate my aloneness but it wouldn't change the nature of my suffering. But if someone came up and said how happy they are I wouldn't feel empathetic happiness. I wouldn't begrudge them their happiness, and I could say I am glad that they are not suffering for their own sake. But I would suffer for my own sake of not being happy and being alone in my suffering.
Suffering therefore seems to me to be essentially lonely. There is nothing from another person that can change it and part of its quality is that it precludes any change in its state, it precludes happiness. I suffer not only from the suffering itself but because of the "stickiness" of it. Happiness is just therefore something like a miracle. It just has to come out of the blue from somewhere, completely inexplicable and unpredictable. If anyone who isn't suicidal could properly understand this they might be able to understand why some people are suicidal. But it seems that being happy also precludes an understanding of what suffering is like. Another layer to the whole thing, ugh.