This is the "permalink" to a post in my test blog (authored using blogger).
Test Blog: OriginalName
Here's the "permalink" after I edited the subject line in the above post.
Test Blog: NewName
Try both. The first now fails. The second will work until I revise the subject line.
These are not Permalinks -- they are Potemkin Links. They look "permanent", but they're fake.
Blogger doesn't support true Permalinks on their post pages.
This is a poor practice. Blogger is encouraging widespread broken links.
There are at lest two things they could do instead:
1. Blogger supports true permalinks on non-post page blogs. They should create a new template tag that would support these old-style in-context links. I prefer in-context permalinks anyway.
2. Blogger could support indirection, so the old link would redirect to the new link.