But that's not what was said. They were banned for failing to answer letters.
No. They were not. They were banned for
failing to follow orders.
There were additional concerns about their failures to answer letters—and indeed, if someone had sat in the capital of my realm for months, receiving all orders and neither following them, nor responding with even a brief note mentioning that they couldn't follow because XYZ, I would be concerned about that too—but the ban explicitly states that they did not follow or respond to orders.
You can ban people for not following orders, but a reasonable effort should be made to be certain that it's not for activity-related reasons.
This is an obligation which runs both ways.
If you have the time to log in every 2 weeks (or more) for
months, you have the time to type up a short note explaining why you are sitting in the capital doing nothing.
From the sounds of things, these characters were sent personal messages and personal orders, and still did not respond in any way. I really don't know what more you want people to do before banning characters like this. Is absence of communication to be taken as proof of inactivity? So...if you respond, you lose, and can be banned, but if you stay silent, you're immune to everything forever?
No. Tom has already rejected reasoning of just this kind.
If you do not follow orders, and you do not autopause, and the ban is not
for inactivity, you can be banned. Period. End of story.