I notice that TB partially displays some of my emails, leaving out critical portions

What "critical portions" are you referring to? I think you're going to have to be very explicit and/or show us a screen shot so we know what you're talking about. You can redact any information you think is sensitive. I have several Yahoo accounts, and while I dislike much about their service, what you describe has never been a problem for me. By the way, despite what Xfinity has been touting about "upgrading" their email service to Yahoo's, they have backtracked, and admit that the migration is voluntary. If you hadn't moved over to Yahoo, your Comcast email would continue to work as usual, at least for the near future. But if you've already made the transition, it's too late to go back.