In the documentation page about "Char.IsSeparator Method"
(url = https://learn.microsoft.com/en-us/dotnet/api/system.char.isseparator?view=net-8.0)
the example has a typo. The character '@' should be accompanied by the '$' character, e.g. @$ or $@ so the relevant line should be:
Console.WriteLine(@$"\u{(int)ch:X4} ({Char.GetUnicodeCategory(ch)})");