Please... especially when LoC and verbosity are some of the advantages of Bicep

By single line assume we mean allowing something like

    addressSpace: {
      addressPrefixes: [ '10.0.0.0/16' ]
    }

One comment I'd have is that as you start to think about single line objects, consider what would happen if you have a bicep linter and your linter converts from single-line to multi-line.

With single line, these would be the same in bicep:

    addressSpace: {
      addressPrefixes: [ '10.0.0.0/16', '10.1.0.0/16' ]
    }
...
    addressSpace: {
      addressPrefixes: [ 
        '10.0.0.0/16'
        '10.1.0.0/16'
      ]
    }

However, a simple code formatting tool may have issues converting between the two since there's not just a white space change.
The linting tool would have to know that the comma is needed in single-line, but not needed in multi-line.

Give that changing lines involved more than just white-space, my suggestion is that you either support just a white-space separator or support both white-space and comma.

This would mean that this would be valid syntax:

    addressSpace: {
      addressPrefixes: [ '10.0.0.0/16' '10.1.0.0/16' ]
    }
...
    addressSpace: {
      addressPrefixes: [ 
        '10.0.0.0/16'
        '10.1.0.0/16'
      ]
    }

Along with

    addressSpace: {
      addressPrefixes: [ '10.0.0.0/16', '10.1.0.0/16' ]
    }
...
    addressSpace: {
      addressPrefixes: [ 
        '10.0.0.0/16',
        '10.1.0.0/16'
      ]
    }

Personally, I support the second syntax (commas) because then each object is a (semi) valid JSON primitive. It would be super nice if it was a valid primitive, but that would require supporting real quote characters :-)