> are there any other languages that support both single and double quotes for string literals? Yes, quite a few like Python, PHP, Fortran, COBOL, Lua, R, Ruby

> are there any other languages that support both single and double quotes for string literals? Yes, quite a few like Python, PHP, Fortran, COBOL, Lua, R, Ruby, Perl, Bourne Shell, Dart, Groovy, etc. Though some only interpolate with one or the other.