Append-only means append-only
Entries are added. They are not edited and they are not deleted. A correction is a new entry that supersedes an old one, and both remain visible.
An audit trail you can quietly rewrite is a log, not an audit trail. The distinction is the whole point of having one.
Decisions carry reasons
Approve or reject with a memo. The reasoning travels with the decision instead of living in someone's memory or a separate thread.
When a figure is questioned later, the answer includes why it was accepted, not only that it was.
Separation of duties where you need it
If your organization requires it, approval can be restricted so that the person who uploaded a document is not the person who signs it off.
This is a control you switch on, not a workflow the product forces on every firm regardless of size.
Isolation by client
Every client is its own organization with its own documents and its own membership list — not a shared pool that a filter carves up.
The audit trail follows that boundary, so one client's history is never visible from another's.