I suppose there are many examples like this. Once I've copied a piece of code from SO but IntellijIDEA was warning me that the semicolon at the end of the line is not correct.
Upon further investigation(I think IntelljIDEA reported Unicode value) I've found out that the 'semicolon' I copied is a Greek character that looks exactly like semicolon.
I wonder how people on vim/emacs deal with situation like this.