What If I Don't Actually Like My Users?

What's wrong with the leading 0 making it octal is that if you have to deal with people who
aren't mathematicians or computer scientists, they probably won't know what octal is. If they
add a leading zero by accident, odds are they'll not be able to figure out what they did wrong
or why the results came out the way they did, and unless you're lucky enough to be standing
over their shoulder while they do it, their bug reports won't have enough information to
replicate it. The difference, to them, between typing in 0507 and 507 is nothing. Hence using
parseInt with a UI is going to cause rare, hard-to-trace problems in exchange for a feature
that no one cares about. (Really, even among computer geeks, few people use octal.)