Jam supports only one kind of comment, which spans for a single line. Since most modern editors have built-in shortcuts to comment out multiple lines of code, this is a non-issue.

# The golden ratio (Phi)
const Phi = 1.618_033_988_749_894_848_204_586

# and it's reciprocal (phi)
const phi = 1/Phi

See also

Language reference on comments