So why bother with this, when compared against AssemblyScript and Grain, both more mature and existing communities?
Moonbit is indeed only developed for less than a year(very fast moving), but it already has a full working IDE, optimizing compiler, fast build system and experimental package manager. We have a dedicated team working on this with professional experience for over a decade, we expect we will reach the maturity on par with Rust in terms of Wasm experience in a couple of years.
The front page doesn't even tell you anything about its unique features. This Moonbit page is a million times better. I might actually try it. I'm not going to try Grain. Why would I?
Hello world and variable declaration syntax isn't going to make me go "ooo interesting! Tell me more!".
I skimmed the guide and found none of the promised "Grain is a new language that puts academic language features to work".
It seems to be a reasonably nice ML/Rust-alike presumably with GC and depending on the unstable WASM GC proposals, though that's mostly a guess - obviously they don't say that anywhere in the main page.
Also we don't known how it will be licensed, but if it's proprietary that could also be a selling point with companies that won't touch Grain's LGPL license.
Prudent companies also require the source code to be kept in a holding that transfers ownership to them if the supplier goes bankrupt.