No problem arises when you switch on the developer option in your smart phone. It never affects the performance of the device. Since android is open source developer domain it just provides permissions which are useful when you develop application. … So no offense if you enable developer option.

Is it bad to turn on developer mode?

No. It doesn’t give any trouble to phone or any thing. But it will give you an access to some of the developer options in mobile like showing touch positions, enabling usb debugging(used for rooting),etc. However changing some things like animation scale and all will reduce the working speed of the mobile.

What happens if you turn on developer mode?

Every Android phone comes equipped with the ability to enable Developer options, which lets you test some features and access parts of the phone that are usually locked away. As you might expect, Developer options are cleverly hidden away by default, but it’s easy to enable if you know where to look.