Continuing the discussion from Imdb embeds broken on other sites:
I just received two mails with practically the same content (that’s weird) due to a response linked above and noticed:
My mail application KMail doesn’t strip off the signature when I reply. The issue seems to be the separator.
KMail claims that RFC compliant is
-- (dash dash space on a single line).
I think I found the source: https://www.ietf.org/rfc/rfc3676.txt (4.3)
However, Discourse uses “—” (triple dash without space) as a separator.
This issue has been raised before: