Inconsistent abbreviations and styles cause viewers to spend extra time reading the lower-thirds and less time absorbing what is being said. As with slates, I prefer substance over style. The goal should be fast and easy readability. Avoid gimmicky fonts. Serif fonts are more readable than sans serif.
Regular weights are easier to decipher than bold ones.
Avoid gratuitous animation in lower-thirds and titles. They only draw atten-tion away from the text. During last year's interminable election coverage, I noticed a lot of waving flag backgrounds on lower-thirds. I would estimate that such animation is distracting enough to cause the viewer to spend approximately 20 percent more time figuring out what the graphic says. That's time spent not absorbing the program's primary content.