Remarks and Notes are stored in their own files and are linked to the bom.  They are entered in BM-A.  These transfer to the work orders.  Remarks are associated with individual parts and print under the component on the traveler.  The Notes are associated with the entire bom and print at the top of the bom on the traveler.
 
Both Remarks and Notes are not static.  Meaning if you change them after a work order has been made then the work order will change too if printed again. (which I think should be changed but that's another thread  )
 
Comments are associated with the work order only.  They are entered in WO-K-B and will print below the component under the remarks.  These are static since they are associated with the work order only.
 

Well, until Lynn & Co make it an option at printing, you could make modify the RTM and make the field invisible.  I think others do this for other fields and have been successful.

Sorry.  You're right.  They are the same field in the RTM.