message-citation-line-function

message-citation-line-function is a variable defined in `message.el'.
Its value is

message-insert-citation-line

• This variable may be risky if used as a file-local variable.

Documentation:
*Function called to insert the "Whomever writes:" line.

Predefined functions include `message-insert-citation-line' and
`message-insert-formatted-citation-line' (see the variable
`message-citation-line-format').

Note that Gnus provides a feature where the reader can click on
`writes:' to hide the cited text. If you change this line too much,
people who read your message will have to change their Gnus
configuration. See the variable `gnus-cite-attribution-suffix'.

You can customize this variable.