Signatures are not being stripped from emails
Postmatic does a very good job of stripping out email signatures but there are certain cases in which we can't do anything.
When email gives no clear distinction between the body (or the comment in this case) and the signature it often sneaks through our filters and the signature will become part of the comment.
A solution for users
You can avoid this by following standard conventions for email signatures. Most importantly give some sort of indication that your email body has ended and the signature/footer begins.
Commonly this is done with a few dashes:
Email signature here
Go ahead and throw some dashes into your signature if you are having this problem.