Since Jellyfin v10.6.0, it’s had a feature called SyncPlay allowing multiple users to watch the same thing at the same time (coordinates pauses, fast forwarding/rewinding, and all that between clients). I’ve used it and it worked like a charm, although I did find that not all clients support it.
I doubt Reddit builds a decent search engine, that doesn’t actually help them at all.
If users can search, they find a previous post pertaining to what they want to see/know and they move on.
If there’s no search, users can’t find old posts or comments so they make new posts about a previously posted topic and more comments are made as other users react. That’s more content, even if low quality from a user perspective, that shows engagement which can be sold to advertisers.
That’s before considering the engineering effort it takes to make a good search engine, constantly fine tune that algorithm, and try to outpace those that are trying to game the search algorithm.
It doesn’t have a speedometer function, but I selfhost Owntracks for personal location tracking with my Android smartphone.
It has a back end that an android app sends location too, and a front end that displays those location points over a map. It can display lines between consecutive points, show a heatmap of the location points, filter location history within windows of time, and more.