This was a helpful writeup. Nim has a lot of really nice features. Are there any problems or things you find lacking?
The idea that thisFunction and this_function are the same might be worse than the problem they're trying to solve. I cannot unfortunately have experience with larg-ish codebases in nim to tell if this would result in an actual problem or not, but the idea that I have to scan between two possible identifiers in the code can be a source of stupid bugs in the same vein as case-insensitive identifiers. On the other hand…
(I'd worry about ambiguities of the experts exchange / expert sex change type, too, but my guess is that they're extremely rare and usually either harmless or instantly caught by the compiler. Still, the mere possibility makes me twitchy.)