I've always assumed that the camp is in the same place that we've identified as a safe spot to sleep in the general area, and we trek back there each night. Though admittedly it would still be odd to leave an unburied body lying around it. If killing companions, or potential companions, to keep things tidy it's clearly best to do it when they're not in your camp!
I've never actually tested this before, but have just confirmed that if you leave a dead companion in one camp, eg the one in the main EA area, their body doesn't follow you to a different camp such as the Underdark one, even if they're stuck in your party. So unless the same camp shows up in different areas - which I kind of hope it doesn't - then it looks like we're safe from actually lugging corpses around with us even if we aren't able to remove them from our party. Which clearly needs fixing too
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