To quote a post, just click the two arrows icon and then click the “quote” option.
Mosseri also said that Threads users on mobile can follow a thread and get notifications on it. This feature apparently hasn’t rolled out for me on iOS — I can’t find it — but I expect I’ll get it soon enough.
These may seem like incremental features, but even small features help making Threads feel like it can be a proper alternative to X (formerly Twitter). That said, X still feels much more live to me; Threads has a ways to go to capture the immediacy that X / Twitter is famous for. (Not forcing the For You feed would help a lot!)