The best I can suggest is that you get him to post something like this:
and check that he really has checked the "Signature is in HTML format" box and that all his HTML tags, attributes and styling are accurately typed and properly opened and closed.
As you know, a missing quote or other punctuation symbol can make all the difference.
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.