This sort of underhanded compliment
can be quite devastating face-to-face
as well. For example:
"With all due respect..."
We all know that nothing good can come of that. You know an insult is about to be delivered, and harshly at that.
"For what it's worth..."
Forget it. At that point, it's a forced compliment, and has lost all sincerity.
"Deep down underneath, you're..."
I think you get the point. No need to elaborate further.