While I agree with the direction, as I had proposed something in this regard in my post in January 2023:
Additionally, we could consider putting up small, unobtrusive banners where relevant (maybe accompanying the question- and answer submission forms).
While the message promises to be useful, I find the specific presented design mockup problematic.
The problem is the placement of that banner, it's literally sitting inside the same textarea I am typing my answer into.
In its spirit, it's similar to those distressing and "impatient" alert banners that some e-mail-address-field validation tools produce, while one is still typing:
"This not a valid e-mail address! Fix it already!"
"I know, smart*ss, I have just started typing the first character, lemme finish first!"
You know the kind.
Now the hereby suggested placement of the banner has a somewhat related problem, and it is that this overly pesky banner™ keeps putting pressure on the user with a humiliating, and thus, highly distressing suspicion, that seems to presume at all times that the user wants to post AI content.
And this suspicion cannot even be resolved by correcting the content in any ways: I presume, the banner stays up all the while the answer is being produced.
One can get rid of that feeling of accusation only by completing the post and leaving the form.
That's humiliating and distressing.
It also does not make sense to put this accusatory piece of UI in between the content that I produce and the tools I use in producing it.
If I rely on any of those WYSIWYG buttons on the top, my mouse has to travel over —and land right next to— this visually prominent, psychologically distressing ("no, I am still not committing that offense that it keeps reminding me about") piece of information.
I do believe that this effect is brought to existence solely by the placement, and proximity of that banner to the textarea device.
Putting the banner just a teeny-weeny bit away, could alter the message:
"We know that you wouldn't post that kind of content. This reminder is necessary, but you are free to tune it out; your contribution is appreciated, and we are thankful for it; here; we recognize and cater to your need to post with dignity."
A different placement, just putting that banner a teeny-weeny bit away, could do away with the problematic effect.
Put it outside of the textarea-device please.