[Users] Threading bug?

[Pierre Fortin]

Hi,

Is this a bug, or me misunderstanding threading...?  All messages in
Inbox and happen to have identical subjects:
>Subject: Re: test

A reply sent several days ago from web interface and Bcc'd back to me as:
>Message-Id: <201112292214.pBTMEwIE004720 at rs103.luxsci.com>
>From: "Pierre Fortin" <pierre at pfortin.com>
>Date: Thu, 29 Dec 2011 22:14:58 +0000

Today, a couple of messages were received as a result of a totally
different test message a few minutes earlier:

>Date: Tue, 3 Jan 2012 17:07:34 -0500
>Importance: Normal
>In-Reply-To: <20120103154734.4833c7fb at pfortin.com>
>References: <20120103154734.4833c7fb at pfortin.com>

>Date: Tue, 3 Jan 2012 17:07:34 -0500
>Importance: Normal
>In-Reply-To: <20120103154734.4833c7fb at pfortin.com>
>References: <20120103154734.4833c7fb at pfortin.com>

These 2 replies are threaded under the above message.

Shouldn't threading be prevented if References are different?

Pierre