Feeding pre-written text into a grammar checker automatically gives the tool free reign to reformat what it deems wrong. The resulting text or sentence is deemed correct - but when someone uses an AI detector and checks the post, it is confirmed to be an AI-generated post. This is what then becomes a debate because actually someone who uses a grammar checker doesn't really want to use AI to post.
There is a way to use tools to correct the grammar or mistakes in a text you've written yourself; you don't need to feed it to a tool and ask it to rectify it, because in that case, it might change the sentences and even words sometimes, and that's a no-go. One should use tools such as Grammarly, which allows you to correct the mistakes you make anywhere in any text box you are writing the content into, and it has different functions, but you should know which ones you need to use and which ones you don't. Specifically, when using Grammarly, you should only correct the mistakes, but if it suggests you changes in your writing, don't accept them, unless you are completely sure that the suggested change isn't going to change a lot of things, especially the words, in your sentence but will only make it sound better.
I use Grammarly myself, and my posts won't be detected as AI-generated. You can give it a try if you want.

I am amazed how theymos never made any statements relating to AI usage in the forum.
It's probably because it hasn't gotten out of hand so far. Most users posting AI-generated content are caught and given neutral tags by the DT, their posts are reported and then deleted by mods. If things start to get out of hand, he might think of something, just like how he came up with
the merit system back in 2018 when spam and spammers were getting out of hand. Even though it didn't completely vanish spam and spammers from the forum, the system still did a great job of stopping undeserving users from ranking up, and that put a full stop to account farming.
