>Most (not all) plain text accounting implementations use signed amounts instead of debits and credits. This makes them "double entry light" perhaps, but it has been a rather successful simplification, intuitive to most newcomers.

They shouldn't do themselves down. I am an accountant and I have used several large systems that do exactly this in the database. It is also by far the preferred way to export a trial balance or gl account from any system to excel. It is the norm in the industry and in no way an innovation of plain text accounting.