This is not a bug, but intended behavior. The rationale behind this is
that with full unicode display, malicious apps could pretend to be other
windows while avoiding software-level confusion via similar glyphs.
This is obviously a major inconvenience if the main/preferred culture of
the user does not make use of the latin alphabet, which is the only one
included in ASCII-censored mode; all other glyphs are replaced with an
underscore.
You can enable utf-8 window titles either for all the system or per-VM
(which I recommend, leaving the "untrusted" ones censored) in a file in
dom0, at /etc/qubes/guid.conf.
The syntax is pretty self-explanatory, however:
* To enable system-wide, add "allow_utf8_titles=true;" inside the
"global:" section
* To enable per-VM, add "allow_utf8_titles=true;" in an
appropriately-named section of the "VM:" section (the name should be the
same as the VM you intend to "uncensor").
The logic is the same as
https://www.qubes-os.org/doc/full-screen-mode/
and actually, since we've already seen this question before on this very
mailing list, I'd suggest adding an article in the documentation about
this setting. Mostly arabic and cyrillic writing users will benefit
(yes, others too, but the requests we've received up to now are from
those cultures).
--
Alex