This goes to the people who build Mender, not to whoever owns the site you were reviewing. Use it when Mender itself is in the way: the dot sitting over something, a panel covering the thing you were looking at, a pin landing somewhere you did not click, a picture that came out wrong.
Something wrong with the site — a typo, a broken link, a layout that has slipped — is a note left on the page itself, with Mender turned on. That reaches the people who can fix it; this does not.