I added https://github.com/PaperMC/Paper/blob/master/Spigot-Server-Patches/0141-Toggleable-Elytra-Wall-Damage.patch a while ago and I'd like to license it under MIT in case someone ever wants to use it for anything.
Instead of calculating the damage taken from hitting a wall, you can disable it in the config.
Running `/save-all flush` would start an infinite loop that prints: ThreadedAnvilChunkSotrage (world): All chunks are saved