Add a comment about bundling multiple frames in single transmission.

src/xmit.c

@@ -597,6 +597,11 @@ static void * xmit_thread (void *arg)
 
 	          case FLAVOR_APRS_DIGI:
 	            xmit_ax25_frames (chan, prio, pp, 1);	/* 1 means don't bundle */
+					// I don't know if this in some official specification
+					// somewhere, but it is generally agreed that APRS digipeaters
+					// should send only one frame at a time rather than
+					// bunding multiple frames into a single transmission.
+					// Discussion here:  http://lists.tapr.org/pipermail/aprssig_lists.tapr.org/2021-September/049034.html
 	            break;
 
 	          case FLAVOR_APRS_NEW: