This feature was one of the most convenient things I’ve ever experienced in any app ever. It’s one of the reasons that Apollo was so endearing to me and others I’m sure. And I’ve never seen any other app that does it. If there is any way this could be implemented it would elevate Memmy above all others.
To clarify, it’s usually just the way I’m holding my phone or resting my hand. While lying in bed, my phone rests on my chest while doomscrolling. One accidental touch of any skin from my hand while holding the top of the phone would scroll all the way to the top of the posts. it was infuriating after scrolling r/all for an hour only to go all the way back to the beginning and have to somehow find my way back to where I was.
Also to clarify your second and third questions, if you never used the feature on Apollo before, this it how it worked: if you scrolled down anywhere, be it in a comments section or down a bunch of posts and tapped the top of the screen, it would take you to the top of the page, the same way it works in most apps and internet browsers. The magic was that if you tap the top again, you would return to where you were when you first tapped the top of the screen. Which is a feature I have never seen except in Apollo.
Ah thank you. Interesting..
Ivory for Mastodon also has it, and I'm assuming it came from their Twitter client (never used it myself though)