Thank you very much! I think the problem would never have shown up had I not decided THAT I WANT IT ALL CAPS LIKE IN THE OLD DAYS WHEN NOBODY HAD THE MONEY FOR SMALLER LETTER. :)
I am actually facing now a strange, different problem: the new uLisp version (2.3) no longer talks with the typewriter over the serial port. Given that I have cloned DUEs only, it will take me a while to figure it out, but 1.9 works just fine.
As to typewriters... well, there's always ebay, of course. If you entertain the idea, let me tell you what I found out:
Mega 2560 are super-nice, even the cloned ones work really well; DUE are terribly capricious, sometimes the serial port working only one direction;
Typewriters are treacherous and tricky: Brother EP 44 works, so does Brother TC 600, and I suspect also Brother WP 600 as well as Wang WP 600 (I did NOT yet test these last two); Brother EP 22 and a lot of others do NOT work - they have "print only" functionality, but cannot send input (yeah, same port, same brand, same series, DIFFERENT functionality...). Not all terminals work, either - I found out, Texas Instruments Silent 703 are normally very "nice" (also DB 25 serial port), but I did NOT get them to work with Arduinos. Good luck! :) EDIT: The Brother EP 44 and TC 600 have one advantage: they can work without ribbons, just on standard thermal paper. This solves the supplies problem which people with Decrwriters and Selectrics face.