Unfortunately, when I have seen this in the context of the Rust project, the result has still been the typical verbose word salad that is typical of chat style LLMs. It is better to use a dedicated translation tool, and post the original along with the translation.
> What about having a plugin in your IDE that rather gives syntax and small code fragment suggestions ("autocomplete on steroids")?
Very good question, I myself consider this sort of AI usage benign (unlike agent style usage), and is the only style of AI I use myself (since I have RSI it helps having to type less). You could turn the feature off for just this project though.
> Does this policy mean that the programmers are also restricted on the IDE and plugins that they are allowed to have installed if they want to contribute?
I don't think that follows, but what features you have active in the current project would definitely be affected. From what I have seen all IDEs allow turning AI features on and off as needed.