When I was 16, I worked at a company that very soon went bankrupt (but that wasn’t my fault). We used PowerBuilder, an environment similar to Delphi, but with a language of its own.
In that language we were allowed to use minus in identifiers. Which means that we had to surround the subtraction operator with spaces (
a-b would be considered a single identifier). At that time I wasn’t in the habit of surrounding operators with spaces. In the options I found a checkbox, that disabled using minuses in variable names, checked it and continued coding happily the way I was used to. Until at the next weekly code merge (which deserves its own post) my code didn’t compile.