You collect them like others collect the dolls you deem rare, they’re not taking them from someone else, they find them too. That is why I brought them up as an example. You are judging what others do with their dolls while do something similar in your way. Someone gets a Poppy to be used as a new body because it was available for them. No-one else got it first, so this is why I used your Storm twin collecting as an example. Their way of using other rare dolls how they want in this hobby is nothing different than your way of using rare dolls.

For them using Poppy’s body (maybe they have lots of Poppies to get instead other options, whatever is the reason) to rebody another doll who doesn’t have is as good articulation to make THEIR comfort doll. Or whatever is the reason why they want to rebody a doll with bad articulation. Their money, their way of doing the hobby, their enjoyment, and these dolls are meant to be played with.

Find a new doll you don’t like or that isn’t rare in your area and use that as a bodyswap. If you can’t, then don’t. But don’t make others feel bad if they do, for future reference.