Looks like I am running into a different issue: while trying to pin down precisely the steps (and the order in which to perform them) needed to remove/rejoin a node, the removal/rejoining exercise was repeated a number of times, and stuck again:
The status of the re-joining node (node4) on other nodes is “I”
The status of the re-joining node on the node4 itself started at “I”, changed to “o”, then stuck there
From the log file for node4, the following entries are constantly being generated:
2017-07-12 10:37:46 PDT [24943:bdr (6334686800251932108,1,43865,):receive:::1(33883)]DEBUG: 00000: received replication command: IDENTIFY_SYSTEM