An example where I disagree, and use 1-letter names daily: arrow functions in both Java and JS.

`usersList.stream().forEach(u -> someSet.add(u))`

It's immediately obvious that u is a user in usersList. I realize that it's debatable if u is really more readable than spelling out user, but I prefer it, and I don't think anyone is going to be confused by it. If the chain does get really long, also, I will spell it out explicitly.