While you have a point with the ugliness of threads and replies I do not like your example with the authenticated media. The reason for the very short deprecation cycle was that it was deemed to be almost a security fix. The Matrix team did not like how their and other's servers were used as CDNs.
Right; it's not unreasonable to want to quickly transfer away from it, but it's still a rather short deprecation cycle compared to everything else I've had to touch never being deprecated; it's not an "example", it's a real thing that actually affects my usage of Matrix (due to being now unable to post images inline in a message (granted, including fixed-URL links wasn't the prettiest thing, but it did work), and having to fully download videos before viewing them from my client that doesn't include video playback, whereas before I could immediately open it in a browser and view it while it's streamed in). Granted, then again, it's the only such occurrence, and probably there's nothing else that could match it in the future.
However many years ago I started work on my matrix client I was rather surprised it ever allowed direct links to media in the first place, but then again Discord had done the same mistake. But at least Discord's solution is more sensible, providing temporary links.
