I say don’t write them at all.
Ignore them.
I have a friend who wrote for daytime soaps (which is why i kept saying to stop insulting them - their twists are far less asinine
) and soaps LOVED getting letters. The angrier, the better. If people take the time to write, no matter what they say in the letter, they are engaged. And that’s what the producers wanted, engagement. They want to know they are living in your head.
Even a letter saying, “bye!” gives them that engagement. They know you care enough to let them know you don’t supposedly care.
Hate/love, the dollar is still green. Indifference is the one thing they want to avoid. If you want to truly starve a writer: don’t give them any feedback. At all. It kills them emotionally.
Besides, Lowe will probably only mock the letters that are sad/angry/saying goodbye.
However, internet communication is so easy and impulsive - it takes a lot more effort to write a letter and send it - that social media is a less dependable bell weather. A project can receive a lot of social media chatter but the correlation between online buzz and people taking action such as watching a show or buying a book is much weaker. But like letters, any buzz is good buzz. It raises awareness.