personally, I'm of the mind to ban it across the board
personal anti-generative ai stance aside, it's also the matter of it effectively cheating tbt gains
I thought of this too after I posted! Historically, the staff have gone through great efforts to prevent exploitation of earning TBT currency. The guy who inputs, "write me 3 reasons why Fire Emblem is awesome", and gets a couple paragraphs with only a few seconds work, has an advantage over everyone else.
I’m very against GenAI like ChatGPT myself, but what would the purpose of such a rule for general posts be? Additionally, how could it even be enforced? “AI detection tools” are notoriously, and arguably intrinsically, unreliable.
I don’t want TBT to be a wasteland of AI slop as much as the next person, but I don’t think this is quite the answer.
NGL, the temptation to do a wee bit of trolling and respond using AI was strong, lol.
Goofiness temporarily aside, the ethical reasons are most important, but you're right that that alone doesn't warrant being banned on a forum. Although, isn't that largely why people were calling for AI art to be banned here, even outside of events? (I agree that it should be, BTW)
I don't wanna go into a whole messy speech about the community's heart being its people, and by rewarding the removal of human elements, the only future is deteriorating into an artificial husk, devoid of true expression and authentic bonds...
... so instead, I'll whine that Mx. ChatGPT user gets more TBT with less effort, and if it doesn't get banned, I'll riot by posting AI slop to fund my collectible habit!
For those curious,
here is a good introductory video on how to spot AI writing.

I was able to tell the posts were AI before I even ran them through software. I know what to look for (as a writer, I have a vested interest in keeping up with it), and with a little bit of research, you can, too!
As more people start picking up the signs of AI speech, if AI isn't discouraged or outright banned, members using the forum as intended will become disgruntled. Some may even turn to AI themselves, because why shouldn't they have that advantage, too? I believe it's in TBT's best interests to take a strong stance before it becomes a widespread issue.
I assume you're worried about innocent users' posts being flagged as AI, but I don't think this would happen very often, if at all. Because it's something that requires discretion, I can see staff erring on the side of caution and focusing on repeat offenders, rather than immediately throwing accusations.
Similar to detecting AI art, identifying AI writing is a skill that will evolve as the technology does. There is always something that gives it away. The signs change over the years, as AI developers try to hide old indicators, but inevitably create new ones. IMO, this is now a necessary skill to acquire for anyone using the internet, like learning how to avoid scams.
No one's going to be hunted down for using an em dash, but when you have multiple red flags indicating AI, that warrants taking a look over their post history, and dealing with it however the staff choose to. For starters, if Community Liaisons (or something similar) become a thing, these people could gently communicate to AI users the harm AI does, since their purpose is to help maintain a healthy community.
Yes, some people will still be able to get away with it, but just because there will be exceptions doesn't mean the rule is useless.