I dislike (slightly) compersion as a catch-phrase turned into a 'must-do'.
I kinda always wondered why you 'need' compersion, if you have respect for your partner in the first place ?
I can respect my partners' need to be out and enjoying himself away from me, without throwing them a good-bye party everytime he goes.
I also have those moments where I am happy for him and his. I liken it much to that feeling when you hear anyone has good news. Getting married, having a baby, etc.
Understanding the need for the descriptor 'compersion' is quite fine by me. It means a very specific type of happiness. I get it. That does not bug me.
However the fact it is sometimes turned into some 'must-do' that everyone should strive for, reeks of that other cult-like persuasion ( meaning devotion in extremes, to a 'ideal' poly).... that can come from a small percentage of people that like to try and overrule all.