All the issues sound more like a them problem than mastadon or cloudflare.
Something's wrong with their setup. Hard to tell as now HN has brought them to their knees
ActivityPub itself could more intelligently cache or display the content but something doesn’t add up if Cloudflare can’t handle that kind of traffic let alone Hacker News traffic.
From the article:
> Presently, we use Cloudflare as our CDN or WAF, as it is a widely adopted solution.
To me, it sounds like the author isn't really familiar with the difference between a CDN and WAF is; or familiar with Cloudflare beyond it being a popular thing they should probably have for that matter.
The images arn't the problem, it's their dynamicly generated page, even if the content is pretty static.
Agreed, and hardly surprising is it that if the site can't cope with link preview traffic that non-trivial page views would be trouble too!