The intended layout of the test network is thus:

test10
  test11
    test30
  test12
  test13

In order to achieve this, I start all servers and then link them by hand thusly:

	On test10:
	/connect test11*
	/connect test12*
	/connect test13*

	On test30:
	/connect test13*

This results in the following /map output from each server, before /squit test10* on test12...

test10 sees:
[09:24:41] * test10.hub.collectiveirc.net  [1 clients]
[09:24:41] * |-test13.hub.collectiveirc.net  [1 clients]
[09:24:41] * |-test12.collectiveirc.net  [1 clients]
[09:24:41] * `-test11.hub.collectiveirc.net  [1 clients]
[09:24:41] *   `-test30.collectiveirc.net  [1 clients]

test11 sees:
[09:24:46] * test11.hub.collectiveirc.net  [1 clients]
[09:24:46] * |-test30.collectiveirc.net  [1 clients]
[09:24:46] * `-test10.hub.collectiveirc.net  [1 clients]
[09:24:46] *   |-test13.hub.collectiveirc.net  [1 clients]
[09:24:46] *   `-test12.collectiveirc.net  [1 clients]

test12 sees:
[09:24:49] * test12.collectiveirc.net  [1 clients]
[09:24:49] * `-test10.hub.collectiveirc.net  [1 clients]
[09:24:49] *   |-test13.hub.collectiveirc.net  [1 clients]
[09:24:49] *   `-test11.hub.collectiveirc.net (102s) [1 clients]
[09:24:49] *     `-test30.collectiveirc.net  [1 clients]

test13 sees:
[09:24:52] * test13.hub.collectiveirc.net  [1 clients]
[09:24:52] * `-test10.hub.collectiveirc.net  [1 clients]
[09:24:52] *   |-test12.collectiveirc.net (103s) [1 clients]
[09:24:52] *   `-test11.hub.collectiveirc.net (106s) [1 clients]
[09:24:52] *     `-test30.collectiveirc.net  [1 clients]

test30 sees:
[09:24:56] * test30.collectiveirc.net  [1 clients]
[09:24:56] * `-test11.hub.collectiveirc.net  [1 clients]
[09:24:56] *   `-test10.hub.collectiveirc.net (117s) [1 clients]
[09:24:56] *     |-test13.hub.collectiveirc.net (106s) [1 clients]
[09:24:56] *     `-test12.collectiveirc.net (110s) [1 clients]

Then, after /squit test10* on test12...

test10 sees:

[09:35:57] * Link with test12.collectiveirc.net cancelled: Server test12.collectiveirc.net closed the connection (<>)
[09:35:57] * *** Notice -- Net break: test10.hub.collectiveirc.net test12.collectiveirc.net (Server test12.collectiveirc.net closed the connection (<>))
[09:36:27] * test10.hub.collectiveirc.net  [1 clients]
[09:36:27] * |-test13.hub.collectiveirc.net  [1 clients]
[09:36:27] * `-test11.hub.collectiveirc.net  [1 clients]
[09:36:27] *   `-test30.collectiveirc.net  [1 clients]

test11 sees:
(no mention of test12 squiting...)
[09:37:10] * test11.hub.collectiveirc.net  [1 clients]
[09:37:10] * |-test30.collectiveirc.net  [1 clients]
[09:37:10] * `-test10.hub.collectiveirc.net  [1 clients]
[09:37:10] *   |-test13.hub.collectiveirc.net  [1 clients]
[09:37:10] *   `-test12.collectiveirc.net  [1 clients]

test12 sees:
[09:35:57] * *** Notice -- Net break: test12.collectiveirc.net test10.hub.collectiveirc.net (Vadtec12)
[09:38:18] * test12.collectiveirc.net  [1 clients]

test13 sees:
(no mention of test12 squiting...)
[09:38:43] * test13.hub.collectiveirc.net  [1 clients]
[09:38:43] * `-test10.hub.collectiveirc.net  [1 clients]
[09:38:43] *   |-test12.collectiveirc.net (586s) [1 clients]
[09:38:43] *   `-test11.hub.collectiveirc.net (589s) [1 clients]
[09:38:43] *     `-test30.collectiveirc.net  [1 clients]

test30 sees:
(no mention of test12 squiting...)
[09:39:10] * test30.collectiveirc.net  [1 clients]
[09:39:10] * `-test11.hub.collectiveirc.net  [1 clients]
[09:39:10] *   `-test10.hub.collectiveirc.net (599s) [1 clients]
[09:39:10] *     |-test13.hub.collectiveirc.net (588s) [1 clients]
[09:39:10] *     `-test12.collectiveirc.net (592s) [1 clients]

Now, after /connect test10* on test12...

test10 sees:
[09:39:58] * *** Notice -- Link with test12.collectiveirc.net established.
[09:39:58] * *** Notice -- Net junction: test10.hub.collectiveirc.net test12.collectiveirc.net
[09:39:58] * Link with test13.hub.collectiveirc.net cancelled: Server test13.hub.collectiveirc.net closed the connection (<>)
[09:39:58] * *** Notice -- Net break: test10.hub.collectiveirc.net test13.hub.collectiveirc.net (Server test13.hub.collectiveirc.net closed the connection (<>))
[09:39:58] * *** Notice -- Completed net.burst from test12.collectiveirc.net.
[09:39:58] * *** Notice -- test12.collectiveirc.net acknowledged end of net.burst.
[09:40:11] * test10.hub.collectiveirc.net  [1 clients]
[09:40:11] * |-test12.collectiveirc.net  [1 clients]
[09:40:11] * `-test11.hub.collectiveirc.net  [1 clients]
[09:40:11] *   `-test30.collectiveirc.net  [1 clients]

test11 sees:
[09:39:58] * *** Notice -- Net break: test10.hub.collectiveirc.net test12.collectiveirc.net (Loop <-- test12.collectiveirc.net (new link is 462 seconds younger))
[09:40:40] * test11.hub.collectiveirc.net  [1 clients]
[09:40:40] * |-test30.collectiveirc.net  [1 clients]
[09:40:40] * `-test10.hub.collectiveirc.net  [1 clients]
[09:40:40] *   `-test13.hub.collectiveirc.net  [1 clients]

test12 sees:
[09:39:53] * *** Connecting to test10.hub.collectiveirc.net.
[09:39:58] * *** Notice -- clock adjusted by adding -1
[09:39:58] * Link with test10.hub.collectiveirc.net established.
[09:39:58] * *** Notice -- Net junction: test12.collectiveirc.net test10.hub.collectiveirc.net
[09:39:58] * *** Notice -- Completed net.burst from test10.hub.collectiveirc.net.
[09:39:58] * *** Notice -- test10.hub.collectiveirc.net acknowledged end of net.burst.
[09:41:09] * test12.collectiveirc.net  [1 clients]
[09:41:09] * `-test10.hub.collectiveirc.net  [1 clients]
[09:41:09] *   |-test13.hub.collectiveirc.net (1043s) [1 clients]
[09:41:09] *   `-test11.hub.collectiveirc.net (1050s) [1 clients]
[09:41:09] *     `-test30.collectiveirc.net (1073s) [1 clients]

test13 sees:
[09:39:58] * *** Notice -- Link with test10.hub.collectiveirc.net cancelled: Loop <-- test12.collectiveirc.net (new link is 461 seconds younger)
[09:39:58] * *** Notice -- Net break: test13.hub.collectiveirc.net test10.hub.collectiveirc.net (Loop <-- test12.collectiveirc.net (new link is 461 seconds younger))
[09:42:17] * test13.hub.collectiveirc.net  [1 clients]

test30 sees:
(no mention of anything that has happened above...)
[09:42:55] * test30.collectiveirc.net  [1 clients]
[09:42:55] * `-test11.hub.collectiveirc.net  [1 clients]
[09:42:55] *   `-test10.hub.collectiveirc.net (599s) [1 clients]
[09:42:55] *     |-test13.hub.collectiveirc.net (588s) [1 clients]
[09:42:55] *     `-test12.collectiveirc.net (592s) [1 clients]

I have confirmed this happens in revision 2084+, 2083- is not plagued by this issue... :(