Mismatched debug2 level output from SSH client when connecting to Teleport hosts vs sshd hosts

What happened: If you run ssh -vv sshd_host, you get all debug1 and debug2 level output shown for your ssh command. This is useful for debugging.

When connecting to a host running sshd with ssh, the debug output essentially stops once you get a terminal. You can use ssh as normal without any extra output until you disconnect.

When connecting to a host running teleport using ssh, you get the debug output during the connection phase, but you also get an extra line of debug2 output every time you type a single character:

gus@zeus:~$ debug2: channel 0: rcvd adjust 1
tdebug2: channel 0: rcvd adjust 1
ydebug2: channel 0: rcvd adjust 1
pdebug2: channel 0: rcvd adjust 1

This effectively means that it's impossible to use ssh with Teleport properly when connected at debug2 level due to the level of spam on screen.

What you expected to happen: debug2 output should be consistent across both Teleport and sshd.

How to reproduce it (as minimally and precisely as possible): ssh -vv sshd_host works fine. ssh -vv teleport_host does not.

Environment

Teleport version (use teleport version): Teleport v4.2.8 git:v4.2.8-0-ga9015b33 go1.13.2
Tsh version (use tsh version): Not relevant here
SSH version: openssh-clients-8.1p1-1.fc31.x86_64
OS (e.g. from /etc/os-release): Fedora 31
Where are you running Teleport? (e.g. AWS, GCP, Dedicated Hardware): Laptop

gravitational / teleport

Mismatched debug2 level output from SSH client when connecting to Teleport hosts vs sshd hosts #3653

Environment