TADS 3 and Unicode

The technical manual says that TADS uses Unicode to represent all strings internally and that all interpreters support UTF-8. Yet all the manuals, examples and source code I’ve found use us-ascii. Even the adv3 library uses us-ascii.

Is there any reason not to use UTF-8 and are there any downsides or potential pitfalls?

I’m using UTF-8 in TADS extensivelly. TADS as a system have full unicode support. QTads works perfectlly, FrobTads works perfectly in plain text and as a web game server, however in curses mode it displays accented characters in inverse and blinking. Biggest problem is that Workbench can’t edit source codes in UTF-8. You can open UTF-8 source files in workbench and step through them in debugger, but all the extended characters will be wrong.