Jump-To Button - What makes it show up?

Does anybody know what causes this button to appear? One of my users sees it but nobody else does, including myself, and I can’t seem to figure out what causes it to show up or not show up.

It’s not a major issue for us, but I’m curious! Thanks.

The Jump to… button is for jumping to a given post within the topic. It shows up as part of the timeline controls on mobile.


This button does not appear for me on a mobile device…

Is that mobile device receiving a desktop view by chance?

Scratch that - it appears for me when clicking the navigator.