Two ways that may be worth trying, based on the access control around line 350 of pubKitBlog.inc.php:
1) if you don’t have a lot of web users, make each of them into a group of one, and give each their own edit page with the snippet call restricting access to their own group. (May need to give them their own manage posts page as well, I’m not sure). They can still share an output folder.
2) add some login at that point in the code to compare the editor ID in the item being edited with the logged-in user ID (could move the block of code at 167-170 to earlier so you catch it when re-editing an item).

KP