[CodesInChaos]

> should be dead simple, it’s a template followed by N values to sub into the template,

CSV without fixed columns would be fine for that.

> require that log message templates be registered in a schema, and then a byte or two can replace the text part of the message.

Pre-registering is annoying to handle, and compression already de-duplicates these very well. Alternatively the logger can track every template logged in this file so far, and assign it an integer on the fly.