OK. I just tried running the game via the Wine compatibility layer, with and without those flags, and interestingly the choppy fonts still appear. So to me this suggests something pretty low level? I also tried running it in a Windows 7 virtual machine, and there the text appeared correctly! Unfortunately its performance was really bad and the game crashed upon generating a new map... Not sure if any of the above is a hint as to what's causing the problem.
There might be other machines I can try this on and I'll do so when I get a chance. I'd rather not give up yet, and I'd love to support your work keeping this wonderful game alive!
That said, considering there's such a lively community. It'll be great to open source the entire game so everyone can help make it better, which will also be profitable for you!
Anyway, thanks for the detailed replies. I'll keep trying for a bit more!