Here in my office we often exchange links to comments by email or instant messaging, ex:

https://mantisbt.org/bugs/view.php?id=22839#c61695

if you visit that link, at least with Firefox and Safari, that floating dark grey header (not sure what it's called) obscures so much of the comment (especially for short comments), that it's not really clear what comment the exchanged link is referring to. See attached image.

Visiting a direct comment link should result in the comment being visible/readable with no addition user action.