Wikipedia has guidance for it as Citing sources. Regarding web links specifically section Handling links and Preventing and repairing dead links.
The Web Archive “Wayback Machine” is available at web.archive.org. It has a “Save Page Now” action too.
https://web.archive.org/web/*/beehaw.org
gives you a history of archived versions of that URL.
The Web Archive “Wayback Machine” is a project from archive.org, which does much more in archiving and accessibility efforts. An alternative service for websites is https://archive.ph/.
I assume you don’t mean keyboard text predictions, which would be a different thing, but the platforms.
It’s a new convenience feature. Something they as a platform can shine with, retain users, and set themselves apart from other platforms.
Having training data is not the primary potential gain. It’s user investment, retention, and interaction. Users choosing the generated text is valid training data. Whether they chose similar words, or what was suggested, is still input on user choice.
It does lead to a convergence to a centralized standard speak. With a self-strengthening feedback loop.