Variables Prefixed with @ or $ fail to render. Should they?

[aanomm]

I noticed variables which are immediately preceded by the @ or $ fail to render. Adding a space between the symbol and variable allows it to works as expected. Is this a bug or known issue, and is there a workaround?

Fails

    $<!-- $price -->
    @<!-- $username -->

Works

    $ <!-- $price -->
    @ <!-- $username -->