Highlighting style?

I’m wondering which highlighting style is more popular. Highlighting is the option to have LingQ color code the words according to how well you know them. At least in iOS, there’s an option now to highlight them differently: Standard, Foreground Color, Underlined, and Off. I was so happy when I found this feature. I immediately set it to off and then got back to reading and found it a much better experience. But I am trying out Underlined now and I like that too. I don’t find the underlining to be so distracting that I can no longer focus on the text. Before, I had been just marking everything ‘known’ so it would stop highlighting words (eventually) but now I don’t have to do that and I’m rating words according to how well I know them again. There’s a lot of words marked known that I really don’t know though. I don’t really mind. What style do you like?