You do not lose any TBT bells for merely editing your posts; what actually happens is an automatic recalculation of the earned bells depending on whether your new post (after the edit) is longer or shorter than the original. If it's longer, you'll gain back the bells you lost plus earn bells for the additional text, and if it's shorter, it'll calculate and redistribute a new total taking into account the lost text. If it's the same length, it'll show that bells were taken, but if you check your log again the system would have credited them back to you post-edit.
The only events where people actually lose bells are if they use the site photo uploader, are given an official warning or infraction, or if they're constantly shortening their posts. Occasionally we staff will have to manually wipe bells, but this is a relatively rare occurrence and the person is always notified when it happens.