Most of the "blabbery omitted" bits are just one-paragraph summaries of the rest of the answer above. It wasn't nonsense, it was just repetitive fluff, and the README was already way too long.
ChatGPT likes mimicking its own previous style, so after it ended its first message with a paragraph like "Overall, porting a Firefox extension to Chrome is doable, but it requires knowledge of the differences...", it kept closing its following messages with similar ending summaries.
The one bit where I refer to it as "nonsensical modification suggestions" was where it suggested that, in addition to changing `chrome.runtime.connect()` to `browser.runtime.connect()`, it told me that:
- I needed to use `document.querySelector`, because Firefox does not support `document.getElementByID` (very clearly not true if you're familiar with DOM APIs)
- I needed to change `classList.add` to `classList.add`, because Chrome supports `classList.add`, but Firefox supports `classList.add` instead (yes those are the exact same thing)
It did make me think for a moment: "what, really, Firefox does not support `getElementByID`? wait, no, of course not, the bot's just saying words."
In this case, it did not get me stuck debugging anything. In other conversations, where I've tried to "play dumb" and follow exactly what it tells me to do, it has sent me down the wrong path. But if you keep telling it "no, that's not working, how can I solve <original problem>", or you give it additional information, it usually corrects course.
I've also seen it say, "well, I don't know what's going on, but the problem must be around this line of code, insert a console log here to see what's going on with this specific value", which was actually good debugging advice, and then you can paste the output of the console log to it, and it takes it into account.