I've seen the app Apollo as the center of the reddit protest (it was mentioned and cited more than any other app in relevant posts). I've also seen many Lemmy clients in development taking inspiration from it.
As a lifetime Android user I've never been able to use it, and I've never gotten a proper answer to "why not just use the official app?" What made it different from the official application and other unofficial clients that consequently made it so popular among Redditors?
In addition to what has already been said, it had several quality of life improvements that weren’t there in the official app at least in the beginning. Such as:
Scrubbing videos over the whole video canvas instead of the tiny dot (paid feature)
Expanding / collapsing comment threads more easily - a feature completely missing from the official Kbin (not Lemmy) web UI and in my opinion crucial
much snappier scrolling
watching videos in the wall view without going into the actual post
swiping back if you accidentally exited thread view
lately saving posts to a specific category
and many more small life improvement features
It was just a client so well planned and executed that using it felt ten times more efficient than the official client.
You can absolutely collapse comment threads in the Lemmy Web UI - it's the minus button next to usernames.
You're on lemmy.world, but this feature is made more obvious in the 0.18 upgrade as they move the collapse button to the left of the avatar/username instead, so it stands out instead of being mixed in with other icons.
I stand corrected. To be honest, I think I just remembered wrong and the one missing collapse is actually kbin. Of course now I’m using wefwef for as long as it works well, so I’m a bit out of touch regarding the capabilities of the og web uis.