Yeah, I’m noticing a lot of missing posts/comments/votes too now. It’s as if the federation protocol is taking a long time to catch up, even if nothing is otherwise blocked. For now I have to browse the communities I like on their host servers through https://lemmyverse.net/, then copy the fediverse URL of the comment I want to reply to, and paste it into my instance’s search box. That usually syncs it up and I can reply then.
lemmy.ml is defederated from lemmynsfw.com, so they cannot exchange any posts anymore. You can see the federated/defederated list at the “instances” link at the bottom of the page. This is the flip side of fediverse: the power to moderate their communities and to chose whom to associate with is given back to the users, but it has the potential to create a “swiss cheeze” social network. To create a user, look for servers that have “free speech” as one of their community values, which would not defederate for ideological/nsfw reasons, and hope no one would defederate from them for being too “free”.
My first impulse as an ex-redditor is to flock to the server with highest population, because I am sheep. I want to see the most content and comments. For me fortunately likewise it took two minutes to figure out that you can see any content from any server. Maybe the server list on join-lemmy.org should show “load percentage” instead of “number of users” :)
It never kicks in for me when it should, but I figured out I can force trigger it manually with the magic SysRq key (Alt+SysRq+F, needs to be enabled first), which instantly recovers my system when it starts freezing from memory pressure.