But that's just your own posts isn't it? Wouldn't the replies from others, which would end up as comments on this author's blog, be in other users' CAR archives in each of their PDSes?
However, atproto data is append-only and cache-friendly. It wouldn't be hard to record historical comments and join them to the ones returned by the live query. (I'm probably just going to script periodic backups for mine and worry about displaying them when/if BlueSky does dissappear.)
It’s a completely valid reason, but All the talk about platform lock in, independent nodes and relay and whatnot is just to make you feel better (I listened to some talks and podcasts but realized that it’s all just window dressing, you can be practically deplatformed at any time, so I’m hazy on the details).
Credible exit matters too. The idea that all of this data is signed, public, and verifiable by anyone helps ensure that the provider is accountable to the community. A provider might decide against enshittifying a product if they're worried about a competitor doing better and taking their place.
Yes, an atproto lexicon will tend to be dominated by a small number of nodes. It's not the perfect distributed system some would prefer, but it is a real improvement on the completely centralized models seen everywhere today.
So if there's a large scale exodus from bluesky, as long as full backfills of the network exist, you'll be able to reconstruct your CAR files, etc even if your PDS dies.
So yes if they die all the comments disappear but people can reconstruct their history and move it to other PDS like blacksky, northsky, or others who are getting ready to start onboarding/open enrollment.
TLDR it'd be a bit rough if they died overnight but if it was a slow death and people had a bit of warning you'd see people move on to other PDS without issue.