I'm pretty sure that the code that decides whether or not to display a [dead] post doesn't consider whether the user had upvoted the post before it became [dead]. Maybe it would be better if it did.
Edit: I can't even click the link on the post you mentioned. Is that normal? That seems especially suspect and somewhat closer to censoring opposing views than I've come to expect from you and HN, Dan.
I don't know but if I had to guess it's because some of these links could be abusive/harmful or spam. I don't think it makes much difference practically in the cases that they aren't since then it's not hard to recover the link with the info left, if you wanted to.
It doesn't address the specific thing but you can see the broader logic here:
I'm pretty sure that the code that decides whether or not to display a [dead] post doesn't consider whether the user had upvoted the post before it became [dead]. Maybe it would be better if it did.