How can I delete this field in the command line? I use command line software to remove unnecessary tags, but I can't get this particular tag deleted, as I don't know precisely how to address it.
Not at all. There are no command line parameters for tag manipulation.
I know that, but I was wondering if you know of any software that can accomplish the feat via the command line. I am working on some scripts. I want to automatically strip some tags, but this one stubbornly refuses to go away.
I thought maybe you would have the technical know-how to recommend something. 
No, sorry, I am quite happy with the GUI features of MP3tag and the built-in scripting functions.
Also, the approach "load once, manipulate many times" seems to me superior to a solution "scan through library again for every manipulation" which is probably the consequence of a commandline solution.
Unfortunately, I need an automated solution with zero human interaction so that's not gonna work.
If you have a dbPowerAmp Reference license you can use the CLI like so
"C:\Program Files\dBpoweramp\CoreConverter.exe" -infile="1.mp3" -outfile="1.mp3" -convert_to="[ID Tag Update]" -delsingle0="COMMENT ID3V1 COMMENT"
It's the only Windows CLI tool I know of that can write those type of comment fields. There is a trial version available at https://www.dbpoweramp.com/dmc.htm
I just discovered that the latest version of ID3 mass tagger can also do this now!
id3.exe -2 -rCOMM:"ID3V1 COMMENT":eng 1.mp3
and also supports recursion e.g.
id3.exe -2 -rCOMM:"ID3V1 COMMENT":eng -R *.mp3