Amazingly fast answer by @GrantSmith :)

Beast modes also accept /* */ as comment blocks, such as this:

/* check to see if the shift is in 
the same day */
(CASE WHEN DATE(`startdate`) = DATE(`enddate`) THEN
/* same day*/
 /* check to see if the start hour is too early */
 (CASE WHEN HOUR(`startdate`)< 9 THEN
 /*move the start date to 9 */
 ADDTIME(DATE(`startdate`),9*60*60)
 /* check to see if the start hour is too late */
 WHEN HOUR(`startdate`)>17 THEN
 /*move it to the next day and start at 9 */
 	ADDTIME(ADDDATE(DATE(`startdate`), interval 1 day),9*60*60)
 ELSE TIMEDIFF(`enddate`,`startdate`)
 END
 )
 ELSE
 /* spans multiple days */
 TIMEDIFF(`enddate`,`startdate`)
 END
)

This is useful if you have a multi-line comment you want to write.