I'll admit up front to being a wasm cynic, but what exactly is the point of having a text editor trapped in a browser sandbox?
It's probably not a huge benefit, but in the same way you can often SSH into somewhere open up Vim make a change and then leave, I can see it being a nice 'clipboard' for my web text. It's not a lot different just to switching to Vim running on your desktop, but I often keep Vim in a separate virtual desktop. I could then also potentially optimise by browser Vim for formatting Markdown / JSON.
It also shows some of the lovely flexibility of Vim.
Plus the browser bindings are never quite right. Although this implementation is a bit buggy, it's actual Vim. So where as it might not have things like multiple buffers, just being able to edit a single buffer in a familiar environment is a really nice feature to have.
I'm certainly going to give this a shot when I next add an answer to SO.