Problem displaying dummy roots

[Tassilo Horn <tsdh@gnu.org>]

Hi all,

I like to show dummy root articles in summary buffers if a thread
contains new messages with different parents.  The configuration for
that is:

  (setq gnus-summary-make-false-root 'dummy)

The problem with this setting is that:

  1) threads with dummy roots are expanded when entering the summary,
     although I have (setq gnus-thread-hide-subtree t).

  2) threads with dummy roots are expanded but are displayed
     incompletely when entering the summary.  An example is this.  I
     enter the summary and there's

--8<---------------cut here---------------start------------->8---
  ┃  ┃     ✘✘✘  ✘✘✘  ✘✘✘     ┃ ○ Re: Why not add some more convenient features to Shell?
 .┃  ┃Milan Bouchet-Valat    ┃ ├─❯  <Today, 10:55>
 .┃  ┃Adam  Tauno Williams   ┃ ╰─❯  <Today, 13:14>
--8<---------------cut here---------------end--------------->8---

     So it looks like there are 2 new messages in this thread.  However,
     if I hide and show the thread again, I see that there are in fact
     three new articles.

--8<---------------cut here---------------start------------->8---
  ┃  ┃     ✘✘✘  ✘✘✘  ✘✘✘     ┃ ○ Re: Why not add some more convenient features to Shell?
 .┃  ┃Amy                    ┃ ├─❯ Re: Why not add some more convenient features to Shell? <Today, 02:06>
 .┃  ┃Milan Bouchet-Valat    ┃ ├─❯  <Today, 10:55>
 .┃  ┃Adam  Tauno Williams   ┃ ╰─❯  <Today, 13:14>
--8<---------------cut here---------------end--------------->8---

Any ideas?

Bye,
Tassilo