I'm a Rust developer but most of the issues are on the frontend UI IMO.
- Constantly refreshing post feeds on the homepage
- Posts changing while you’re commenting
- Momentarily showing you logged in as someone else
- Long delays in comments and votes being applied - sometimes forcing you to refresh the page with no confirmation
- Wasted side space on the built-in themes on desktop
I wish there were a simple UI like Hacker News - https://github.com/IronOxidizer/lemmy-lite was one attempt at that but it isn't maintained or finished.
I don't think the instance-level "silencing" from Mastodon is a good idea tbh. It leads to more free-loading of content hosting and less of a federation.