Just discovered that admins are removing resource-content on the subreddit. Both the DPRK and China megathreads that are in the sidebar have been removed, probably others too.
I doubt this is unique to only /r/communism, /r/communism101 is probably going to be hit as well.
Do remember that archive.org sometimes excludes and removes things.
https://theoutline.com/post/4653/the-internet-s-collective-memory-is-unstable-as-hell
https://gizmodo.com/when-the-internet-archive-forgets-1830462131
https://archiveteam.org/index.php/List_of_websites_excluded_from_the_Wayback_Machine
They are mostly reliable but if there is something you really care about then keep a local copy.
An example: https://web.archive.org/web/http://clarkesworldmagazine.com/fall_01_20
Same page can be found here: http://archive.is/oXDEt (controversial but good story if you can read past its title)