The jump to top floating button is very useful on mobile. Although as a Wikipedian, I have to scroll down many time (e.g. to check the page history, latest topic on a talk page) which is sometimes physical pain, especially when I am reading a huge project/talk page. An optional jump to bottom would be great.
I'd say that this also calls for some extra thought: are there things that should be moved from the bottom of the page to the top? Such as categories, etc.?
If I recall correctly, the last editor's name was shown at the bottom, but was moved to the bottom by popular demand.
Curious about the exact problem here. If page history, categories and talk are moved to the top of the page, is a jump to bottom button still become useful?
Does the similar T197718 help with the problem we're trying to solve (or could it be adapted to do so - make sure to check the prototype on the task!)