When displaying a message that has Enigmail's protected header information (like a message to myself), Enigmail replaces the Subject to the protected value.
This leads to a duplication of the "Re:" prefix.
The attached image shows this before and after the click on the message in the list. See the Subject display in the message display area, it's correct.
Here's the (shortened) source of the displayed message:
Subject: Re: test
To: Bernd Wurst bernd@XXXXXXX
From: Bernd Wurst bernd@XXXXXXX
Openpgp: preference=signencrypt
Date: Tue, 24 Apr 2018 14:54:57 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
Thunderbird/52.7.0
Mime-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="=_YYY
This is a MIME-formatted message. If you see this text it means that your
E-mail software does not support MIME-formatted messages.
--=_YYY
Content-Type: multipart/mixed; boundary="TsAckZfKCfYh5rSE49vvcnlKEk8iuQ4tJ";
protected-headers="v1"
From: Bernd Wurst bernd@XXXXXX
To: Bernd Wurst bernd@XXXXXX
Subject: Re: test
--TsAckZfKCfYh5rSE49vvcnlKEk8iuQ4tJ
Content-Type: text/plain; charset=utf-8
Content-Language: de-DE
Content-Transfer-Encoding: quoted-printable
Am 24.04.2018 um 14:54 schrieb Bernd Wurst:
Am 24.04.2018 um 14:54 schrieb Bernd Wurst:
test
=20
=20
I noticed this too. I haven't found a solution yet.
fixed on master and 2.0-branch.