If you re-view a post after it's soft deletion, you can still soft delete it.
If you do that, there is nothing that happens. The reason isn't being edited too.
I think this should be "fixed" by
1. Not being able to soft delete anymore
2. Updating the delete reason
I would say this is by design, as those that can permanently delete a post can select to view the soft-deleted post by a moderator, and then select the delete once again to permanently delete it if they choose.
If you select multiple threads, say "all" in a threadlist, and you have 1 that's already soft deleted, you don't want the inline moderation to stop working, because of it.
I agree it should be working as it currently does.