Question about stderr output containing carriage return External

[Joshua Rogers]

Hi all,

I have recently only discovered that openssh prints lines to stderr
separated by CLRF pairs, and am trying to understand where this
behavior comes from.

This behavior can be seen here:
--snip--
$ ssh u at u 2>&1 | sed -n l
ssh: Could not resolve hostname u: Name or service not known\r$
--snip--

I have seen section 11.3 from rfc4253, but am unsure whether that is
the origin of this behavior. Is a "Debug Message"(SSH_MSG_DEBUG)
considered anything that is logged on stderr?

Any insights welcome!

Cheers,
Josh