Dear 100 Hour Board,
If my patronus is a thestral but I haven't witnessed death, can I see my patronus? Can other people?
Your patronus is a thestral?! Are you okay? What happened to you that would make having an ominous horse that only appears to people that have seen death is your patronus? I’m no patronus expert but I’ve got a lot of questions about this, and a lot questions about you and your well being.
Given the current confusion that JK Rowling is going through, I don't think she'll get around to answering my Twitter DM, and even if she did... could we really trust her answer? So here's some thoughts, based on my conversations with self-proclaimed HP experts.
It's unlikely that a thestral would be your patronus in the first place... because it doesn't make any sense to have your patronus be a creature you haven't ever seen/don't know what it looks like. Your patronus is affected by your life experiences, as we've seen by how they can change based on emotionally significant event. So, from the get-go, it seems pretty unlikely that this scenario would happen in the first place. Additionally, it's not common to have a patronus that is a magical creature. Most are just normal earthly animals. The most obvious magical example is Dumbledore's phoenix patronus.... but that's part of his family's lore, so it seems that perhaps there are special rules that apply to him.
So, let's say hypothetically that you are a rare exception to the general rules, and you not only have a magical creature patronus, but it's a thestral. From what I've discussed with others, the consensus is that because it's only a representation of the real thing, you would indeed be able to see it, and so would other people. It doesn't necessarily possess the same magical properties that would require the witness to have seen death. Also, since perhaps this thestral patronus may be part of your family's legends, I would think at least YOU would be able to see it because it's special and specific to you, and maybe there's something about your bloodline that would allow you to see it even if you hadn't seen death. There's a possibility that other people would be able to see it, but I believe it's less likely.