When writing a post: If you fill out the title field, then start editing the body of the post, the perma-link preview will match your title (in slug form). So far, so good.
But let's say you decide to change the title before publishing--in that instance, the perma-link preview will stay the same as the original title, but when the post is actually published the perma-link (slug) will turn out to reflect the later, edited title. The same issue applies when leaving the title field blank at first--but in this case the slug is auto-assigned as the post number, and not updated when the user goes back to change the title--but the slug turns out reflecting the title anyway when the post is published.
(I know that this differs when one actually edits the perma-link and hits save.)
Judging by the behavior I've described, at first I actually thought that there might be a feature that allowed the user to create the slug first and then go back and change the post title to something different, but then I realized that such a feature was illusory and what we really have here is a bug, however minor, that can be confusing and cause link breakage.
Fixing this (by having the slug updated each time the post is auto-saved, perhaps?) would improve consistency and predictability and create a more intuitive interface.
