STOX_REPLY_TYPE_WITHOUT_QUOTES

I'm seeing this rule: STOX_REPLY_TYPE_WITHOUT_QUOTES
Catching on legitimate mail.

It's a meta rule and right enough it catches this line:

Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original

AND does NOT match either:

__HS_SUBJ_RE_FW Subject =~ /^(?i:re|fw):/
or
rawbody __HS_QUOTE /^>

SCORING.
 0.2 STOX_REPLY_TYPE        STOX_REPLY_TYPE
 1.9 STOX_REPLY_TYPE_WITHOUT_QUOTES STOX_REPLY_TYPE_WITHOUT_QUOTES

As legitimate mail, it's picking up just over 2 points for this - and
I'm wondering what the sender is possibly doing wrong here?