The description of how to allow windows to have UTF8 characters in the title bar is outdated, as it refers to the file /etc/qubes/guid.conf which is deprecated. I have updated this description according to the current documentation of qvm-features.
This documentation, however, is somewhat unclear, and I would like to make it more understandable. Can anyone help there? @adw???
I found that the Qube Manager allows setting this feature, and it works as expected. So I changed the documentation accordingly.
There remains, however, the question of how to set the feature globally, which behaves inconsistently with the (correct) behavior of the Qube Manager. I have (for this time) just omitted the corresponding sentence from the documentation page. But as this seems to be somewhat connected to issue #7730 just opened by @Demi , I described the inconsistency there - maybe that helps a bit.
In the meantime, @marmarek has somewhat cleared this confusion, and I have updated the documentation once again. I hope that it is now correct. Thanks a lot for your help!