Context

Something the application attached to a turn rather than a person writing it: a brief, a protocol, the page somebody was looking at.

It is a row of its own because it is not what anyone said, and showing it as a message would put an application's words in a person's mouth. What the name means, and whether a reader should see it at all, is the host's: the name is carried through untouched and nothing here knows any host's vocabulary.

A host decides what a reader sees; it does not decide what was sent. Everything here reaches the page, so a stylesheet that hides a context still ships it — in the document, in the source a reader can view, and to a screen reader. Anything a viewer must not have is left off the message before it is sent, never hidden after it arrives.