Is the 'concurrent editing' checking working?
Take a look at the edit history of SO 3780075. There are 5 or more edits (one of them mine) within a single minute - the question went to Community Wiki in record time. I certainly did not get notified of concurrent editing activity.
For the record: the first two edits were made in the same second, and 56 seconds after the question was asked. The next two were a sluggish 70 and 71 seconds after the question was asked. The next was at 93 seconds; the sixth at 2 minutes 1 second; and the seventh edit (eighth revision) was a whole 3 minutes 8 seconds from when the question was asked.
- Question (revision 1) asked at 45:19
- Revisions 2 and 3 both timed at 46:15
- Revision 4 at 46:29
- Revision 5 at 46:30
- Revision 6 at 46:52
- Revision 7 at 47:20
- Revision 8 at 48:27
Some questions are still waiting for their first views when this one had gone to Community Wiki.