That’s because your data is stored locally, so special characters in the title = special characters in the filename, which isn’t possible. Small but very worthwhile tradeoff.
The file title is the file name so what ever's invalid for a file name is invalid as a title.
But there are some work arounds:
- Disabling inline title and setting the document title yourself with what ever characters
- Using aliases (in the YAML front matter) so you can search a document with it's special character title, and auto-set a link's custom text