“is it really so strange that I end up feeling sad for person #2 and my own feelings of pain/hurt lessen after hearing someone else’s problem?”
No, sometimes realizing how much worse it could have been makes u feel fortunate. But to me u just seem to be feeling bad about their pain instead of urs.
“Is it wrong for someone to share their pain to show that my pain is not so bad or not worth feeling bad over?”
Yes. No one should tell u ur feelings are “wrong” or try to stop u from feeling something. That doesn’t actually work and doesn’t make people feel better. Validation is what makes people feel better. You are entitled to feel whatever ur feeling.