I believe the bell losses with journal edits happen because of the way edits work. When you edit a post, it first takes away the bells you originally earned for the post, then gives you back the amount of bells that the post is worth after the edit. So: If your post is longer after the edit, you get more bells back than the amount that was taken, and if the post is edited to be shorter you get fewer bells returned and you'll end up losing a few.
So far so good, right? That sounds fair. But: You can only get bells from your island journal 24 hours after your last post.
This means that if you make a post to your island journal, and if you then go to edit another post, it seems to take away the amount of bells that the post was originally worth (like it should) but it fails to give you back the new amount (because you already made a post and got bells in the last 24 hours).
The workaround: if you care about your bells, wait 24 hours after your last post to make the edit. It seems to have worked for me so far.
Also: I've also edited a whole bunch of posts in my island journal quickly after another, I think the bell loss happens only once. Maybe you can only lose bells every 24 hours too? Either way the system seems to be a bit broken.
@Dunquixote Feel free to point the staff to this post in your CTS thread as a possible cause.
I'm also tagging @Livia and @Tinkeringbell because they may want to know.