(Started replying to Griatch, went on a tangent, it'll fit better here I think. Skip the first paragraph to go straight to LPC advocacy :D)
Last time I looked at Evennia it wasn't even in alpha, it just started out (and I was a jealous teenager that wanted to do everything himself, too). Since it was so long ago, I only remember (roughly) the basic ideas and some funny interactions on the mailing list, where the creator tried to convince some would-be contributor that no, you don't need money to start such a project... :)
I do remember LPMUD stuff way better. You're right that, at least in the beginning and on the MUD I played and later coded on, the most common way of writing code was... a clone of `ed`. Really, the line-oriented editor, the one just a step before "magnetic needle and a steady hand". You wrote the code in Notepad, then ran `ed` over telnet, pasted the code and observed it being sent, line by line. You quickly learned what \n is and why it's important thanks to that :) Sometimes you missed a semicolon, so you also naturally learned about `s` and regexes, to ease the pain a little. At some point, though, admins figured out the permissions and it became possible to upload code via FTP. Progress!
As for the architecture, the only "hard"-coded part was the "driver", which was just an interpreter/VM for LPC, plus some code to handle network and disk IO. Everything else was written in LPC. LPC was unique in a bunch of ways: it was gradually typed, it was object-oriented but didn't have classes and used prototypal (and multiple!) inheritance on top of providing #include. Imagine a cross between Ruby and JavaScript coupled with object database/object persistence built-in. Everything was an object, and the system was fully reflective - you could manipulate and change parts of the running system from within. Even the source files on disk were objects within the system - as soon as the file got created, it was already an entity you could manipulate with code (that `ed` clone was written in LPC, too).
It was incredibly powerful and fun way of coding. Version control was a problem, of course - since code was a dynamic, run-time construct, versioning just files wouldn't cut it. It's the same problem Smalltalk images suffer from. It's possible to solve, but you'd have to code the version control system into the driver, and guys capable of hacking on the driver were few and far in between. Once again, simpler triumphed - although modern Smalltalks do offer VCSes comparable in features with mainstream ones.
Much, much later I realized that what made it all possible was a version of "become" method from Smalltalk: a way to replace one object with another completely and invisibly. The lack of this primitive operation was what made all my attempts to fully recreate the environment in Python fail (along with problematic object model in Python 2.x, but that's another story). In the end, some ten years later, I learned both Smalltalk and Self, and realized I could get what I wanted by writing a rudimentary telnet server in Pharo. By then, though, MMORPGs ate most of the mindshare that kept MUDs alive, and I got distracted with other projects. I did a few prototypes while learning strange programming languages, but always stopped at ~2-3k loc and never finished any of them. I used these as tools for learning only, believing there's nobody who'd be interested in this way of playing by programming (or programming by playing.)
> I wish there was something similar today.
TL;DR: I researched ~20 programming languages and environments, and got reasonably close to the LPC experience in two of them: Io and Smalltalk. Io is not very actively maintained (last I checked), but there are mature, stable, and free Smalltalk implementations out there. An added bonus is that you get MUD client along with the environment and you don't need to build Web-based admin interface (most Smalltalks provide a GUI).
I have some code I can share if you're interested; I get the same urge to build this thing from time to time, but never really followed through with any of the attempts. Though, I suspect the story would change a little if even just one other person was interested :)