This is an odd edge case I encountered today. If spoiler text is in a quote, you can blur/unblur it as normal. If you expand the quote, you can also blur/unblur the spoiler text in the expanded quote. However, once you close the expanded quote (so the post looks like it originally did), the quoted spoiler text gets stuck in whatever state you had it in before expanding the quote. I’ll create a post right below this to demonstrate.
This is some spoiler text to test with.