"Handling texts that are larger than available memory. Ropey is an in-memory data structure."
That seems to make it of dubious use, not really suitable for a well-engineered text editor.
The fact that it's UTF-8 only is also a serious problem since files can contain arbitrary byte sequences.
What text editor do you use where loading a large text file doesn't put that entire text file in memory? In a world where even sub-$100 devices have gigabytes of memory, this doesn't seem even remotely problematic.
Devices with lots of ram can fit huge files, devices with very little ram can still fit very large, but not gigabytes-huge files. You're not going to fire up VS Code on pi 2 and load a 5GB log file, but you are going to fire up a simpler editor and open a 100MB log file. So as long as you can fit files that make sense for your device in memory, so why would "it loads files into memory" be a problem?
You're just making up numbers to fit the conclusion. For example, the only alternative is either a 5G or 100M file. But in reality, just like you have many tabs in a browser, each eating their 100M away, you'll be opening multiple log files. So those cool sounding "several gigs" is actually very constrained, for example: 3G is "several gigs", but on Windows you will be almost always memory-constrained with a few browsers running (web, chat, etc) and you won't have much to open a few of those 100M log files
Same to you: do you actually? Because I don't use a single device where I'm loading more into memory than it's designed for. If you're a 100 tab kind of person, there's help, you don't have to suffer yourself in silence. And if you open so many logs at the same time as to memory constrain the device you're using, that's the proverbial "are you sure you're not doing it wrong?"
So again: which editor are you using that's not currently loading your logs in memory? Because that's still not been answered. Hell even emacs and vim do that, so what are you even doing? what are you using that makes this solution loading data into memory not okay when even the most hardcore unix user's "pry it from my cold dead hands" tools already do exactly the same?
What kind of wild use case involves editing a text file larger than modern ram?