Sometime on Jan 20, Manoj Srivastava assembled some asciibets to say:
Fix your client for the last time or stop quoting me!
If you would point out what exactly is broken, I would be
happy to oblige. Seems like my MUA is correctly generating the attribution.
Your MUA is using his email address as the attribution rather than his name. Since pipermail only filters out email addresses from the header, that means that you're effectively putting his email address up on the net for everyone to see.
Change your quoting style to use sender's name rather than email.