^[3] If the main purpose of underlining of links in most output formats it to indicate that the underlined text is “clickable”, given that links rendered in man pages are not “real” hyperlinks that users can click on, it might seem like there is never a good reason to have link contents underlined in man output.

In fact, if you suppress the display of inline link references (by setting man.links.are.numbered to zero), there is no good reason to have links underlined. However, if man.links.are.numbered is non-zero, having links underlined may (arguably) serve a purpose: It provides “context” information about exactly what part of the text is being “annotated” by the link. Depending on how you use mark up your content, that context information may or may not have value.