I use Berkeley mail (/usr/bin/mail) on an iMac. It has just started behaving in strange ways. If I type "~v", to open an editor, I get "[LogLevel VERBOSE]" or sometimes "[LogLevel DEBUG]" and the editor doesn't open. I get the same behavior running heirloom mailx. Any idea why this might be happening and how I can stop it? (I'm not a power user and know little about logging.) Somewhat mysteriously, this new behavior coincided exactly with an upgrade to Mavericks, not on the machine running Unix mail, but on the machine from which I remotely ssh to that machine. The machine running Unix mail hasn't been upgraded: uname -v yields "Darwin Kernel Version 11.4.0: Mon Apr 9 19:32:15 PDT 2012; root:xnu-1699.26.8~1/RELEASE_X86_64".
OK, I figured it out. It's a new escape sequence ("~v" for changing the logging level) in the latest version of ssh. I fixed it by changing the escape character.