Cannot remove underlining

[TAB]

In badUnder.odt, why is 'F2' underlined? highlighting it and hittint ^u, or using Format>Character>FontEffect/Underlining does nothing.
On the first line, the 2nd C (in CctWC) has no such problem.

[RoryOF]

Highlight the F2, then in /Format /Styles and Formatting select Character Styles (2nd icon from left). Internet link should be selected there. Right click on this and select Modify, then Font Effects tab. Change Underlining to "none" (you may have to scroll up to find this, it is at top of the options offered.)

I cannot say why F2 differed from C - I played with the usual direct formatting changes, and could get C to change but not F2.

[TAB]

It looks like Issue 123220.
https://bz.apache.org/ooo/show_bug.cgi?id=123220

[TAB]

But C is also a hyperlink, and I can underline it at will.
Both C and F2 point to OO documents; F2 has nothing to do with a web page.