Characters representing non-ASCII Unicode characters (even in strings) gets
converted into question marks when a sketch is saved.

For instance, the following sketch
String a = "καλημέρα";
when saved will immediately appear as
String a = "????????";

You're at the mercy of how Java handles your default character set. But as
it happens, this is something that I plan to fix for 0136, so that UTF8 is
used for all files.

In the meantime, use ASCII, and for non-ASCII characters use Unicode escape
sequences: \uXXXX and so on.

fixed for release 0141.