Reddit's caches are set up to only ever return the last 1,000 of anything. So for example - you can't scroll past 1k items on /new, and if you save more than 1k posts then you'll have to unsave some to retrieve the others.
If this extension only edits comments, it'll only touch the most recent 1k. You would need to retrieve the older ones with a Pushshift replacement like this: https://pullpush.io/. But that also shows how ineffective this is. We still have public reddit archives (like Pullpush and https://github.com/ArthurHeitmann/arctic_shift) which contain comments as they were originally posted. This isn't gonna be a problem for Google.
If this extension only edits comments, it'll only touch the most recent 1k. You would need to retrieve the older ones with a Pushshift replacement like this: https://pullpush.io/. But that also shows how ineffective this is. We still have public reddit archives (like Pullpush and https://github.com/ArthurHeitmann/arctic_shift) which contain comments as they were originally posted. This isn't gonna be a problem for Google.