I have had this happen to me due to a single quote. When the reader hits a single quote it goes into strikeout mode. It has happened to me when I have students submit sql files and they copy the questions over from a word doc. I do not have this issue in my c++ classes or python classes even though they also have single quotes nor are there issues on with a single quote in sql that was written within the editor - only those copied over, so I think it must be a smart quote.

Now if I can just figure out why the latest version of canvas (2/14) won't allow me to make annotations to cpp, sql or py files - which is why I am here :).