Gnus, compile and grep buffers are lists. They are not really like
hypertext in that there is no or little text to click on that is not
mouse sensitive. This makes it inconvenient to click to set the mouse
I can't comment on Gnus, which I don't use. In Compilation and Grep
modes, only the file names and line numbers respond to mouse-1. They
also show a mouse face.
Perhaps we should underline them to make them look more like a link.
How about that?