Been using Fedistar for a few days now. It does a lot right, but it is not good at displaying threads.
When I click on a post in Sengi, it (usually) shows me the whole thread. Fedistar sometimes does that, but usually it just shows me the post, without any replies, or the post that it's replying *to*. Sengi fails sometimes, but it's much more reliable.
I also really wish Fedistar would tag bot accounts and visually indicate whether a post has replies, like Sengi does.