If there's one nasty coding habit that gets me riled up every time it has to be coding with non English words. This probably won't mean much to the English speaking crowd, but here in Israel, and in other non English speaking countries, junior developers often choose to give their parameters, class names, database tables and sprocs names that, although written in English, are words in their mother tongue.
For example, I've come across code that looks like this:
Obviously, this is totally unreadable to anyone who does not speak Hebrew. Actually, it's hard to read even if you know Hebrew since you're used to read English, not translating it in your head to Hebrew. Ugh. Here's an easier to read translation: