When would the u tag be confused as a link?

In the “Applied Visual Design: Use the u Tag to Underline Text” section, it noted to “try to avoid using the u tag when it could be confused for a link.”

When would the u tag be confused as a link and what is the alternative to using the u tag?

underlined text on the internet is generally assumed to be a link. exceptions could be: headlines and subheads, resume formatting, stuff like that.

I don’t recommend using the u tag at all. Use the CSS text-decoration property instead. Other than that, a blue underlined text usually gives the impression that’s it’s a link. If it is in the middle of a paragraph, you can turn of the color so that it’s not confused. Or you can make it bold. In headings it’s usually fine. But why underline it when CSS has so much more to offer, don’t you think?