There's multiple issues reported, only the first one appears to be UTF-16 related and all of the reported issues trigger the issue with simply opening a malicio

There's multiple issues reported, only the first one appears to be UTF-16 related and all of the reported issues trigger the issue with simply opening a malicious text file. The referenced conversion presumably happens eagerly so the editor can operate in utf8 in memory. I think that's more severe than you suggest; it means that someone could craft malware and all it would take is get someone to view the file in notepad++ to run an exploit.