There is specifically, precisely, not a single word in Sec. 230 of the CDA as pertains to the 'size' of the website, its userbase, or its "Millions of communications" LOFL.
FR receives "Millions of communications" every month: scrapes, ddos attempts, pings, bounce-backs, and actual user activity -- if you could call this thread "actual user activity" -- if you don't believe me, ask John right here, if you think just maybe one of you could compose the question intelligently enough.
You know, on second thought, don't bother John.

Can you parse that down to just "user activity" meaning someone trying to communicate something to other people?
Also, if you are of a mind to do so, can you put up the same stats for Twitter, so we can compare apples to apples?