Almost all the things I have favourited on this site has been some extremely niche comment that would not be archived in whatever system we come up with. They have been specific comments that are useful for me to reference, to use in argument with others, or to reword again and again in propaganda.

The entire value of /r/genzhou was similar, being able to search it with pushshift search and type in any subject topic and get back incredibly high value comment responses.

The personal value isn't even the major issue here. The value in the historic archive of content comes from search results, a massive amount of traffic comes from weird old threads on various internet forums that end up showing up in weird searches that people do. Narrowing down the amount of content that could get seen or found via the search engine results completely compromises the site's ability to reach potential new users. For better or worse all websites must build themselves around the understanding that the vast majority of their traffic is going to come from search engine results pages and failure to do so just guarantees being niche and unfindable. Unexposed to anyone.

Yes it's an infosec risk. But the site existing at all is one. Anyone can scrape and mirror the entire site if they want to, people already do just that for reddit (unddit.com) where you can see content deleted by mods and users, pushshift also keeps an archive of all your reddit content and probably has many comments that you've deleted from your various reddit accounts, assuming you use reddit of course. We're kidding ourselves if we think that this site isn't already being archived by intelligence services given that the subreddit was literally in an ASPI paper which is a thinktank literally founded by the Australian gov.