Incoming heal/Uninterruptable display

[Teliko]

A friend of mine recently noticed other players have an option in their game that shows incoming heals on their health bar and also when an uninterruptable heal, such as a holy paladin in bubble, displays a shield icon around the cast bar. For whatever reason, he is unable to active these options for his main character. He can get them working on his alts, and it's definitely a default UI function, but we don't seem to be able to find it anywhere. We've even tried restoring all default setting and disabling every addon, but have achieved nothing.

Does anyone have any idea how to activate these?

[Seerah]

Is his main character a healer and/or has an interrupt spell/ability?

[Teliko]

He has an interrupt ability and being a healer seemingly doesn't make a difference, we experimented with different classes and different specs.