ASCII 60-63 is just <=>?

You probably mean 28-31 (∟↔▲▼, or ␜␝␞␟)

Unless this is octal notation? But 0o60-0o63 in octal is 0123

I've wanted to do that but don't you have compatibility problems? What can read/import files with those deliminters? Don't people you are working with have problems?