"Images above 2,400px width or over 10MB will be downscaled, resampled and, if applicable, converted to WEBP for default viewing." If you are wondering why it does not seem much difference when viewing here. Below the image: "Download original" shows the resolution it is really. I assume you would have to click "Download original" for each picture or "Archive Download" "Original" if you have enough GP.
I was surprised by the absence of the second speech bubble on the first page compared to the lower-res version. Then there are a few other differences, but they are only minor edits.