Non-working characters might be due to that the database holding these messages does not use unicode character set. One feature of the unicode is that it has separate codes for the ohm sign ? (alt+2126) and big greek omega ? (Alt+03A9). Degree character ° is in 8-bit ISO charsets, so perhaps that's why it is saved, also same for ±.
I think that EDA software authors or development teams are not the most concerned about unicode support in the software
Although it would be nice to use correct symbols as there is no longer need to settle for 8 bit character set due to lack of support. Windows has used unicode for a quite long time now, and I'm sure that Linux and other similar OS's have similar situation nowadays.
Regards,
Janne