When I log into my server via SSH, I receive the following error:
There seems to be something wrong with the locale settings. When I execute the "locale" command, I see similar errors:
I'm logging in via macOS, if that makes any difference, to "web523.webfaction.com". Thanks a lot in advance for any help!
Finally, I found the solution for this problem: it's described in detail here.
In a nutshell, my LC_CTYPE environment variable is set to "UTF-8", which is not supported on the server I'm connecting to. By default, SSH tries to recreate those environment variables (LC_*) on the server, which fill fail in this case (this is the error I am seeing).
The workaround is to uncheck "Set locale environment variables on startup" in the macOS terminal profile you are using (via "Terminal - Preferences - [any profile] - Advanced").
Why this is necessary on one of my macs, but not on the other — that's another question, but I'll leave it at that. ;-)