We already know about some important, major categories of RC diff such as "Language link added" which are expected to not show up in our visible diffs because they change (in the example of language link) sitelinks or something else meaningful about the page.
This might involve running a pyspark module on the analytics cluster to gather this information, if it wasn't provided by the recentchanges API.
Be careful not to pull any private data into our results files. Aggregate before storing (eg. to a boolean "is language link"), if there's any risk.