When I'm reviewing someone else's code I frequently have to explain the same thing (to different people) in multiple code reviews. Currently I refer people to my note in an earlier pull-request like this:
See details in this pull-request <link>, search for "copy-and-swap idiom is not applicable to this case", if you fail to find then scroll down to the bottom of the page, this will result in loading more contents of the page, repeat multiple times if necessary.

I want to be able to refer people like this:
See details here <link>.

For this to work, after I posted my note in the pull-request, I need to have (in the bottom line of the note, next to the buttons "Reply", "Edit", "Delete", "Create task") a button "Share" (or "Link") pressing which will result in copying to the clipboard the direct link to this particular note (and showing on the screen the window with the message: "The link has been copied to the clipboard").