This has been an issue since the game began. That tells me that while there might be "simple" ways to fix this as suggested here, implementing them likely requires a fair bit of coding.
There is a simple work around which I use EVERY time I sell: Move everything I want to keep out of my bag (wear it or put it on a packer) and I ONLY sell out of my bag, NEVER off a packer.
Having said that, it "should be" relatively easy to give sellable items a check box (like are used for chat tabs) that flags the item unsellable just as mission items are. Of course, it is relatively easy to walk to the top of Everest compared to walking to the Moon. ;)
There is a simple work around which I use EVERY time I sell: Move everything I want to keep out of my bag (wear it or put it on a packer) and I ONLY sell out of my bag, NEVER off a packer.
Having said that, it "should be" relatively easy to give sellable items a check box (like are used for chat tabs) that flags the item unsellable just as mission items are. Of course, it is relatively easy to walk to the top of Everest compared to walking to the Moon. ;)
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Eldest, Order of the White Lotus