If you're working on very slow network connections, or the network just dies entirely, it's not uncommon for Emacs just to hang entirely. You then have to kill Emacs from another terminal. At the time I was running exwm (an Emacs window manager), which made the whole thing even more painful. Emacs is powerful, but polish is not its strong point.
That said, this was a few years ago now. Things may have improved in 26.1 when threads were introduced, and async got even easier.
It's written for sigbovik 2021 [1][2], which is very much a joke conference. Other papers this year were "Lowestcase and Uppestcase letters: Advances in Derp Learning" and "On the dire importance of mru caches for human survival (against Skynet)".
I can't deny it! Though Urn was much more a "I want to do something with Lua" project, than something targeting CC. That being said, I know people have got the compiler running on various other fantasy consoles.
Urn effectively tries to be it's own language which sits on top of the Lua runtime. I've tried to take the nicest bits of Lua and combine it with macros and a little more compile-time checking. Though I'm not entirely sure how successful I've been...
Urn was is very much an experimental project for me: part of me wanted to see how much I could do with as little syntax. Consequently Urn has comparatively few "special forms", but meaning it generates less idiomatic Lua.
Fennel is much more an alternative syntax to Lua. Most Lua constructs have a corresponding Fennel form, meaning the generated code looks more "like Lua". Lua interop is also much nicer: Urn requires you to declare all variables, so you have to jump through hoops to use external libraries. With Fennel you can just go ahead like you would with Lua.
That said, this was a few years ago now. Things may have improved in 26.1 when threads were introduced, and async got even easier.