[SifJar]

It not only makes it slightly harder to read - it can also make it slightly harder to modify.

For example, if all variables in a code base are camelCase but one variable StartsWithUpper, chances are every time you reference that variable in a future code change you'll call it startsWithUpper and then hit an error (depending on the language, either at compile time or run time), and have to go back and fix it. So it adds a little time to development in that way. Negligible, but non-zero