Mangled "Re:" in i18n subject header

Hello!

Look, here is the subject from a mailman-managed
mailing list:

Subject: [Bug]
=?koi8-r?B?UmU6IFtCdWddIFJlWzJdOiBbQnVnXSBSZTogW0J1Z10gUmU6IFtCdQ==?=
=?koi8-r?B?Z10g8NLPxMHF1NPRINPMwdfRztPLycog28vBxg==?=

Let me decode it:

import sys, email.Header
print email.Header.decode_header(sys.stdin.read())

[('Subject: [Bug]', None), ('Re: [Bug] Re[2]: [Bug] Re:
[Bug] Re: [Bug] \xf0\xd2\xcf\xc4\xc1\xc5\xd4\xd3\xd1
\xd3\xcc\xc1\xd7\xd1\xce\xd3\xcb\xc9\xca
\xdb\xcb\xc1\xc6', 'koi8-r')]

Look how many "Re:"s re there!

The problem arise when Mailman adds list tag (in this
case [Bug]) to an *encoded* header. Mailman must decode
the header and check for "Re:" and list tag in the
decoded header.

All mailing lists that I know are guilty with the bug.
Let Mailman be the first that fixes it! Thank you.