Lars Ingebrigtsen <larsi@gnus.org> writes:

> I'm not sure I understand the question -- if you set
> `gnus-build-sparse-threads', does Gnus not do that?

Cool, I didn't know about this setting!

This helps! Although, is it possible to hide the sparse messages (with Q
mark)? So the tree would be similar, but the gaps wouldn't be visible. 

Because, when I run (gnus-summary-limit-exclude-marks "Q"), the tree structure
seems to be flattened again.

I've been taking a peek at the code and it doesn't seem easy to me to
achieve this, because the way the gnus-build-sparse-threads function
works, is to just create the missing messages, so all the other code can
just rely on "all messages being there".

That was I meant in my original question: There are multiple message ids
in the References header, but Gnus only uses the last message in that
list to build the threads. I'd like Gnus to build threads using the
"closest grandparent" algorithm.

E.g. a tree like this:

<Message-ID: A@example.com>
  <Message-ID: C@example.com; References: A@example.com, B@example.com>
    <Message-ID: D@example.com; References: A@example.com, B@example.com, C@example.com>
  <Message-ID: E@example.com; References: A@example.com, B@example.com, non-existing@example.com>
  



-- Toon