

If communities were global instead of instance-based, instance mods/admins would likely still be able to moderate posts and comments hosted on THEIR instance (which may be important to confirm to local laws), but they wouldn’t be able to moderate the ENTIRE discussion.
There are likely some advantages to this (such as discussion not being able to be stifled by overeager or politically extremist mods), but it would also mean there is no way to globally enforce any particular rule (unless all instance admins agree on it).
While I’m not entirely convinced that Trunky is the best choice of names, I do agree with your overall reasoning. Mastodon was always an awkward choice for a name and probably hurt adoption quite a bit, despite all the cute elephant cartoons people ended up making. Even Pleroma (an alternative server implementation compatible with ActivityPub) sounds cooler than Mastodon, despite also being three syllables long.